diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 497e0f7767..cd8dd376fe 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -276,7 +276,7 @@ jobs:
       - name: Install brew tests dependencies
         run: |
           brew install subversion
-          Library/Homebrew/shims/scm/svn --homebrew=print-path
+          brew sh -c "svn --homebrew=print-path"
           which svn
           which svnadmin
 
diff --git a/Library/Homebrew/shims/mac/super/gem b/Library/Homebrew/shims/mac/super/gem
new file mode 120000
index 0000000000..a38a43ef7a
--- /dev/null
+++ b/Library/Homebrew/shims/mac/super/gem
@@ -0,0 +1 @@
+ruby
\ No newline at end of file
diff --git a/Library/Homebrew/shims/mac/super/rake b/Library/Homebrew/shims/mac/super/rake
new file mode 120000
index 0000000000..a38a43ef7a
--- /dev/null
+++ b/Library/Homebrew/shims/mac/super/rake
@@ -0,0 +1 @@
+ruby
\ No newline at end of file
diff --git a/Library/Homebrew/shims/mac/super/ruby b/Library/Homebrew/shims/mac/super/ruby
new file mode 100755
index 0000000000..91921781ff
--- /dev/null
+++ b/Library/Homebrew/shims/mac/super/ruby
@@ -0,0 +1,12 @@
+#!/bin/bash
+# System Ruby's mkmf on Mojave (10.14) and later require SDKROOT set to work correctly.
+
+source "$HOMEBREW_LIBRARY/Homebrew/shims/utils.sh"
+
+try_exec_non_system "$SHIM_FILE" "$@"
+
+if [[ -z "$SDKROOT" && -n "$HOMEBREW_SDKROOT" ]]; then
+  export SDKROOT=$HOMEBREW_SDKROOT
+fi
+
+safe_exec "/usr/bin/$SHIM_FILE" "$@"
diff --git a/Library/Homebrew/shims/scm/git b/Library/Homebrew/shims/scm/git
index 65ecc55237..a33d4ea433 100755
--- a/Library/Homebrew/shims/scm/git
+++ b/Library/Homebrew/shims/scm/git
@@ -3,87 +3,15 @@
 # This script because we support $HOMEBREW_GIT, $HOMEBREW_SVN, etc., Xcode-only and
 # no Xcode/CLT configurations. Order is careful to be what the user would want.
 
-set +o posix
-
-quiet_safe_cd() {
-  cd "$1" >/dev/null || { echo "Error: failed to cd to $1" >&2; exit 1; }
-}
-
-absdir() {
-  quiet_safe_cd "${1%/*}/" && pwd -P
-}
-
-dirbasepath() {
-  local dir="$1"
-  local base="${2##*/}"
-  echo "$dir/$base"
-}
-
-realpath() {
-  local path="$1"
-  local dir
-  local dest
-
-  dir="$(absdir "$path")"
-  path="$(dirbasepath "$dir" "$path")"
-
-  while [[ -L "$path" ]]
-  do
-    dest="$(readlink "$path")"
-    if [[ "$dest" = "/"* ]]
-    then
-      path="$dest"
-    else
-      path="$dir/$dest"
-    fi
-    dir="$(absdir "$path")"
-    path="$(dirbasepath "$dir" "$path")"
-  done
-
-  echo "$path"
-}
-
-executable() {
-  local file="$1"
-  [[ -f "$file" && -x "$file" ]]
-}
-
-lowercase() {
-  echo "$1" | tr "[:upper:]" "[:lower:]"
-}
-
-safe_exec() {
-  local arg0="$1"
-  if ! executable "$arg0"
-  then
-    return
-  fi
-  # prevent fork-bombs
-  if [[ "$(lowercase "$arg0")" = "$SCM_FILE" || "$(realpath "$arg0")" = "$SCM_REAL" ]]
-  then
-    return
-  fi
-  if [[ "$HOMEBREW" = "print-path" ]]
-  then
-    local dir="$(quiet_safe_cd "${arg0%/*}/" && pwd)"
-    local path="$(dirbasepath "$dir" "$arg0")"
-    echo "$path"
-    exit
-  fi
-  exec "$@"
-}
-
-SCM_FILE="${0##*/}"
-SCM_REAL="$(realpath "$0")"
-SCM_DIR="$(quiet_safe_cd "${SCM_REAL%/*}/" && pwd -P)"
-
-if [[ "$1" = --homebrew=* ]]
+if [ -z "$HOMEBREW_LIBRARY" ]
 then
-  HOMEBREW="${1:11}"
-  shift
+  echo "${0##*/}: This shim is internal and must be run via `brew`." >&2
+  exit 1
 fi
 
-case "$(lowercase "$SCM_FILE")" in
+source "$HOMEBREW_LIBRARY/Homebrew/shims/utils.sh"
+
+case "$(lowercase "$SHIM_FILE")" in
   git)
     if [[ -n "$HOMEBREW_GIT" && "$HOMEBREW_GIT" != git ]]
     then
@@ -98,21 +26,10 @@ case "$(lowercase "$SCM_FILE")" in
     ;;
 esac
 
-brew_prefix_version="$(quiet_safe_cd "$SCM_DIR/../../../../../bin" 2>/dev/null && pwd -P)/$SCM_FILE"
+brew_prefix_version="$HOMEBREW_PREFIX/bin/$SHIM_FILE"
 safe_exec "$brew_prefix_version" "$@"
 
-brew_repo_version="$(quiet_safe_cd "$SCM_DIR/../../../../bin" && pwd -P)/$SCM_FILE"
-safe_exec "$brew_repo_version" "$@"
-
-IFS=$'\n'
-for path in $(type -aP "$SCM_FILE")
-do
-  if [[ "$path" != "/usr/bin/$SCM_FILE" ]]
-  then
-    safe_exec "$path" "$@"
-  fi
-done
-unset IFS
+try_exec_non_system "$SHIM_FILE" "$@"
 
 if executable "/usr/bin/xcode-select"
 then
@@ -129,19 +46,19 @@ then
   fi
   if [[ -z "$popup_stub" && "$xcode_path" != "/" ]]
   then
-    path="$(/usr/bin/xcrun -find "$SCM_FILE" 2>/dev/null)"
+    path="$(/usr/bin/xcrun -find "$SHIM_FILE" 2>/dev/null)"
     safe_exec "$path" "$@"
   fi
 fi
 
-path="/Applications/Xcode.app/Contents/Developer/usr/bin/$SCM_FILE"
+path="/Applications/Xcode.app/Contents/Developer/usr/bin/$SHIM_FILE"
 safe_exec "$path" "$@"
 
 if [[ -z "$popup_stub" && "$HOMEBREW_MACOS_VERSION_NUMERIC" -lt "101500" ]]
 then
-  path="/usr/bin/$SCM_FILE"
+  path="/usr/bin/$SHIM_FILE"
   safe_exec "$path" "$@"
 fi
 
-echo "You must: brew install $SCM_FILE" >&2
+echo "You must: brew install $SHIM_FILE" >&2
 exit 1
diff --git a/Library/Homebrew/shims/utils.sh b/Library/Homebrew/shims/utils.sh
new file mode 100644
index 0000000000..7d90d7b697
--- /dev/null
+++ b/Library/Homebrew/shims/utils.sh
@@ -0,0 +1,94 @@
+set +o posix
+
+quiet_safe_cd() {
+  cd "$1" >/dev/null || { echo "Error: failed to cd to $1" >&2; exit 1; }
+}
+
+absdir() {
+  quiet_safe_cd "${1%/*}/" && pwd -P
+}
+
+dirbasepath() {
+  local dir="$1"
+  local base="${2##*/}"
+  echo "$dir/$base"
+}
+
+realpath() {
+  local path="$1"
+  local dir
+  local dest
+
+  dir="$(absdir "$path")"
+  path="$(dirbasepath "$dir" "$path")"
+
+  while [[ -L "$path" ]]
+  do
+    dest="$(readlink "$path")"
+    if [[ "$dest" = "/"* ]]
+    then
+      path="$dest"
+    else
+      path="$dir/$dest"
+    fi
+    dir="$(absdir "$path")"
+    path="$(dirbasepath "$dir" "$path")"
+  done
+
+  echo "$path"
+}
+
+executable() {
+  local file="$1"
+  [[ -f "$file" && -x "$file" ]]
+}
+
+lowercase() {
+  echo "$1" | tr "[:upper:]" "[:lower:]"
+}
+
+safe_exec() {
+  local arg0="$1"
+  if ! executable "$arg0"
+  then
+    return
+  fi
+  # prevent fork-bombs
+  if [[ "$(lowercase "$arg0")" = "$SHIM_FILE" || "$(realpath "$arg0")" = "$SHIM_REAL" ]]
+  then
+    return
+  fi
+  if [[ "$HOMEBREW" = "print-path" ]]
+  then
+    local dir="$(quiet_safe_cd "${arg0%/*}/" && pwd)"
+    local path="$(dirbasepath "$dir" "$arg0")"
+    echo "$path"
+    exit
+  fi
+  exec "$@"
+}
+
+try_exec_non_system() {
+	local file="$1"
+  shift
+
+	IFS=$'\n'
+	for path in $(type -aP "$file")
+	do
+	  if [[ "$path" != "/usr/bin/$file" ]]
+	  then
+	    safe_exec "$path" "$@"
+	  fi
+	done
+	unset IFS
+}
+
+
+SHIM_FILE="${0##*/}"
+SHIM_REAL="$(realpath "$0")"
+
+if [[ "$1" = --homebrew=* ]]
+then
+  HOMEBREW="${1:11}"
+  shift
+fi