use skip_deps_check? instead of ignore_deps? hack

We previously set `ignore_deps?` as true for DependencyInstaller to
avoid duplicated dependencies resolution. (See a9fc82aea30506eeacbddeb8b53fb85de8acb9d4)

However, this will cause problem when pouring bottle of a dependency is
failed. In this case, it will try to build dependency from source but
failed due to uninstalled build deps for this formula.

Another disadvantage for using `ignore_deps?` hack is we cannot
distinguish users passing `--ignore-dependencies` flag from we are in
`DependencyInstaller`.

So, let's differentiate these using `skip_deps_check?`

Library/Homebrew/formula_installer.rb

@@ -56,6 +56,10 @@ class FormulaInstaller
     @pour_failed   = false
   end
 
+  def skip_deps_check?
+    ignore_deps?
+  end
+
   # When no build tools are available and build flags are passed through ARGV,
   # it's necessary to interrupt the user before any sort of installation
   # can proceed. Only invoked when the user has no developer tools.
@@ -97,7 +101,7 @@ class FormulaInstaller
   end
 
   def prelude
-    verify_deps_exist unless ignore_deps?
+    verify_deps_exist unless skip_deps_check?
     lock
     check_install_sanity
   end
@@ -120,7 +124,7 @@ class FormulaInstaller
   def check_install_sanity
     raise FormulaInstallationAlreadyAttemptedError, formula if @@attempted.include?(formula)
 
-    unless ignore_deps?
+    unless skip_deps_check?
       unlinked_deps = formula.recursive_dependencies.map(&:to_formula).select do |dep|
         dep.installed? && !dep.keg_only? && !dep.linked_keg.directory?
       end
@@ -159,7 +163,7 @@ class FormulaInstaller
       raise BuildToolsError.new([formula])
     end
 
-    unless ignore_deps?
+    unless skip_deps_check?
       deps = compute_dependencies
       check_dependencies_bottled(deps) if pour_bottle? && !MacOS.has_apple_developer_tools?
       install_dependencies(deps)
@@ -364,15 +368,8 @@ class FormulaInstaller
   end
 
   class DependencyInstaller < FormulaInstaller
-    def initialize(*)
-      super
-      @ignore_deps = true
-    end
-
-    def sanitized_ARGV_options
-      args = super
-      args.delete "--ignore-dependencies"
-      args
+    def skip_deps_check?
+      true
     end
   end