diff --git a/Library/Homebrew/extend/os/mac/extend/ENV/super.rb b/Library/Homebrew/extend/os/mac/extend/ENV/super.rb
index ca1dbf2c10..c928f4dda1 100644
--- a/Library/Homebrew/extend/os/mac/extend/ENV/super.rb
+++ b/Library/Homebrew/extend/os/mac/extend/ENV/super.rb
@@ -107,16 +107,17 @@ module Superenv
 
   # @private
   def setup_build_environment(formula = nil)
-    if formula&.requirements&.find { |req| req.is_a? XcodeRequirement }
-      self["HOMEBREW_SDKROOT"] = MacOS.sdk_path_if_needed && MacOS::Xcode.sdk_path
-      self["HOMEBREW_DEVELOPER_DIR"] = MacOS::Xcode.prefix
-    else
-      self["HOMEBREW_SDKROOT"] = MacOS.sdk_path_if_needed&.to_s
-      self["HOMEBREW_DEVELOPER_DIR"] = if MacOS::CLT.installed? && MacOS::CLT.provides_sdk?
-        MacOS::CLT::PKG_PATH
-      else
+    sdk = formula ? MacOS.sdk_for_formula(formula) : MacOS.sdk
+    if MacOS.sdk_root_needed?
+      self["HOMEBREW_SDKROOT"] = sdk.path
+      self["HOMEBREW_DEVELOPER_DIR"] = if sdk.source == :xcode
         MacOS::Xcode.prefix
+      else
+        MacOS::CLT::PKG_PATH
       end
+    else
+      self["HOMEBREW_SDKROOT"] = nil
+      self["HOMEBREW_DEVELOPER_DIR"] = nil
     end
     generic_setup_build_environment(formula)
 
diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index 705c868bca..80d6c5705e 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -1352,8 +1352,7 @@ class Formula
     args << "-DHAVE_CLOCK_GETTIME:INTERNAL=0" if MacOS.version == "10.11" && MacOS::Xcode.version >= "8.0"
 
     # Ensure CMake is using the same SDK we are using.
-    sdk = MacOS.sdk_path_if_needed
-    args << "-DCMAKE_OSX_SYSROOT=#{sdk}" if sdk
+    args << "-DCMAKE_OSX_SYSROOT=#{MacOS.sdk_for_formula(self).path}" if MacOS.sdk_root_needed?
 
     args
   end
diff --git a/Library/Homebrew/os/linux.rb b/Library/Homebrew/os/linux.rb
index 82472db5ac..0c5d025859 100644
--- a/Library/Homebrew/os/linux.rb
+++ b/Library/Homebrew/os/linux.rb
@@ -53,6 +53,10 @@ module OS
       languages.first
     end
 
+    def sdk_root_needed?
+      false
+    end
+
     def sdk_path_if_needed(_v = nil)
       nil
     end
diff --git a/Library/Homebrew/os/mac.rb b/Library/Homebrew/os/mac.rb
index 6163d11f23..5343d7def4 100644
--- a/Library/Homebrew/os/mac.rb
+++ b/Library/Homebrew/os/mac.rb
@@ -74,6 +74,17 @@ module OS
       @active_developer_dir ||= Utils.popen_read("/usr/bin/xcode-select", "-print-path").strip
     end
 
+    def sdk_root_needed?
+      if MacOS::CLT.installed?
+        # If there's no CLT SDK, return false
+        return false unless MacOS::CLT.provides_sdk?
+        # If the CLT is installed and headers are provided by the system, return false
+        return false unless MacOS::CLT.separate_header_package?
+      end
+
+      true
+    end
+
     # If a specific SDK is requested:
     #
     #   1. The requested SDK is returned, if it's installed.
@@ -94,6 +105,13 @@ module OS
       @locator.sdk_if_applicable(v)
     end
 
+    def sdk_for_formula(f, v = nil)
+      # If the formula requires Xcode, don't return the CLT SDK
+      return Xcode.sdk if f.requirements.any? { |req| req.is_a? XcodeRequirement }
+
+      sdk(v)
+    end
+
     # Returns the path to an SDK or nil, following the rules set by {.sdk}.
     def sdk_path(v = nil)
       s = sdk(v)
@@ -109,10 +127,7 @@ module OS
       # 4. On CLT-only systems with a CLT SDK, where headers are provided by the system, return nil.
       # 5. On CLT-only systems with a CLT SDK, where headers are not provided by the system, return the CLT SDK.
 
-      # If there's no CLT SDK, return early
-      return if MacOS::CLT.installed? && !MacOS::CLT.provides_sdk?
-      # If the CLT is installed and headers are provided by the system, return early
-      return if MacOS::CLT.installed? && !MacOS::CLT.separate_header_package?
+      return unless sdk_root_needed?
 
       sdk_path(v)
     end
diff --git a/Library/Homebrew/os/mac/sdk.rb b/Library/Homebrew/os/mac/sdk.rb
index a3a8dcf83d..156c41812d 100644
--- a/Library/Homebrew/os/mac/sdk.rb
+++ b/Library/Homebrew/os/mac/sdk.rb
@@ -5,11 +5,12 @@ require "os/mac/version"
 module OS
   module Mac
     class SDK
-      attr_reader :version, :path
+      attr_reader :version, :path, :source
 
-      def initialize(version, path)
+      def initialize(version, path, source)
         @version = OS::Mac::Version.new version
         @path = Pathname.new(path)
+        @source = source
       end
     end
 
@@ -20,14 +21,14 @@ module OS
         path = sdk_paths[v]
         raise NoSDKError if path.nil?
 
-        SDK.new v, path
+        SDK.new v, path, source
       end
 
       def latest_sdk
         return if sdk_paths.empty?
 
         v, path = sdk_paths.max { |a, b| OS::Mac::Version.new(a[0]) <=> OS::Mac::Version.new(b[0]) }
-        SDK.new v, path
+        SDK.new v, path, source
       end
 
       def sdk_if_applicable(v = nil)
@@ -48,6 +49,10 @@ module OS
 
       private
 
+      def source
+        nil
+      end
+
       def source_version
         OS::Mac::Version::NULL
       end
@@ -78,6 +83,10 @@ module OS
     class XcodeSDKLocator < BaseSDKLocator
       private
 
+      def source
+        :xcode
+      end
+
       def source_version
         OS::Mac::Xcode.version
       end
@@ -98,6 +107,10 @@ module OS
     class CLTSDKLocator < BaseSDKLocator
       private
 
+      def source
+        :clt
+      end
+
       def source_version
         OS::Mac::CLT.version
       end