fix(env): tweak build-time env vars preparation

Author: jimeh

build-emacs-for-macos

@@ -506,7 +506,7 @@ class Build
   def env_CFLAGS
     return @env_CFLAGS if @env_CFLAGS
 
-    env = []
+    env = ENV.fetch('CFLAGS', '').split
 
     env << '-O2'
 
@@ -532,13 +532,29 @@ class Build
       env += ENV['NIX_CFLAGS_COMPILE'].split
     end
 
-    @env_CFLAGS = env
+    clean_env = []
+    skip_next = false
+    env.each_with_index do |flag, index|
+      if skip_next
+        skip_next = false
+        next
+      end
+
+      if flag == '-isystem' && env.size > index + 1
+        clean_env << "-isystem #{env[index + 1]}"
+        skip_next = true
+      else
+        clean_env << flag
+      end
+    end
+
+    @env_CFLAGS = clean_env.map(&:strip).reject(&:empty?).compact # .uniq
   end
 
   def env_LDFLAGS
     return @env_LDFLAGS if @env_LDFLAGS
 
-    env = []
+    env = ENV.fetch('LDFLAGS', '').split
 
     # Ensure library re-linking and code signing will work after building.
     env << '-Wl,-headerpad_max_install_names'
@@ -555,13 +571,13 @@ class Build
 
     env += ENV['NIX_LDFLAGS'].split if use_nix? && ENV['NIX_LDFLAGS']
 
-    @env_LDFLAGS = env
+    @env_LDFLAGS = env.map(&:strip).reject(&:empty?).compact # .uniq
   end
 
   def env_LIBRARY_PATH
     return @env_LIBRARY_PATH if @env_LIBRARY_PATH
 
-    env = []
+    env = ENV.fetch('LIBRARY_PATH', '').split
 
     if options[:native_comp]
       env += [
@@ -573,37 +589,49 @@ class Build
 
     env << '/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib'
 
-    @env_LIBRARY_PATH = env
+    @env_LIBRARY_PATH = env.map(&:strip).reject(&:empty?).compact.uniq
   end
 
   def env_PKG_CONFIG_PATH
-    return [] if use_nix?
+    return @env_PKG_CONFIG_PATH if @env_PKG_CONFIG_PATH
 
-    @env_PKG_CONFIG_PATH ||= [
-      File.join(brew_dir, 'lib/pkgconfig'),
-      File.join(brew_dir, 'share/pkgconfig'),
-      File.join(brew_dir, 'opt/expat/lib/pkgconfig'),
-      File.join(brew_dir, 'opt/libxml2/lib/pkgconfig'),
-      File.join(brew_dir, 'opt/ncurses/lib/pkgconfig'),
-      File.join(brew_dir, 'opt/zlib/lib/pkgconfig'),
-      File.join(
-        brew_dir,
-        'Homebrew/Library/Homebrew/os/mac/pkgconfig',
-        OS.version.to_s
-      )
-    ]
+    env = ENV.fetch('PKG_CONFIG_PATH', '').split
+
+    unless use_nix?
+      env += [
+        File.join(brew_dir, 'lib/pkgconfig'),
+        File.join(brew_dir, 'share/pkgconfig'),
+        File.join(brew_dir, 'opt/expat/lib/pkgconfig'),
+        File.join(brew_dir, 'opt/libxml2/lib/pkgconfig'),
+        File.join(brew_dir, 'opt/ncurses/lib/pkgconfig'),
+        File.join(brew_dir, 'opt/zlib/lib/pkgconfig'),
+        File.join(
+          brew_dir,
+          'Homebrew/Library/Homebrew/os/mac/pkgconfig',
+          OS.version.to_s
+        )
+      ]
+    end
+
+    @env_PKG_CONFIG_PATH = env.map(&:strip).reject(&:empty?).compact.uniq
   end
 
   def env_PATH
-    return [] if use_nix?
+    return @env_PATH if @env_PATH
 
-    @env_PATH ||= [
-      File.join(brew_dir, 'opt/make/libexec/gnubin'),
-      File.join(brew_dir, 'opt/coreutils/libexec/gnubin'),
-      File.join(brew_dir, 'opt/gnu-sed/libexec/gnubin'),
-      File.join(brew_dir, 'bin'),
-      File.join(brew_dir, 'opt/texinfo/bin')
-    ]
+    env = ENV.fetch('PATH', '').split
+
+    unless use_nix?
+      env += [
+        File.join(brew_dir, 'opt/make/libexec/gnubin'),
+        File.join(brew_dir, 'opt/coreutils/libexec/gnubin'),
+        File.join(brew_dir, 'opt/gnu-sed/libexec/gnubin'),
+        File.join(brew_dir, 'bin'),
+        File.join(brew_dir, 'opt/texinfo/bin')
+      ]
+    end
+
+    @env_PATH = env.map(&:strip).reject(&:empty?).compact
   end
   # rubocop:enable Naming/MethodName,Naming/VariableName
 
@@ -612,22 +640,14 @@ class Build
 
     env = {
       'CC' => use_nix? ? 'clang' : '/usr/bin/clang',
-      'PATH' => [
-        env_PATH, ENV.fetch('PATH', nil)
-      ].flatten.compact.reject(&:empty?).join(':'),
-      'PKG_CONFIG_PATH' => [
-        env_PKG_CONFIG_PATH,
-        ENV.fetch('PKG_CONFIG_PATH', nil)
-      ].flatten.compact.reject(&:empty?).join(':')
+      'PATH' => env_PATH.join(':'),
+      'PKG_CONFIG_PATH' => env_PKG_CONFIG_PATH.join(':')
     }
 
     if options[:native_comp]
-      env['CFLAGS'] = [env_CFLAGS, ENV.fetch('CFLAGS', nil)]
-                      .flatten.compact.reject(&:empty?).join(' ')
-      env['LDFLAGS'] = [env_LDFLAGS, ENV.fetch('LDFLAGS', nil)]
-                       .flatten.compact.reject(&:empty?).join(' ')
-      env['LIBRARY_PATH'] = [env_LIBRARY_PATH, ENV.fetch('LIBRARY_PATH', nil)]
-                            .flatten.compact.reject(&:empty?).join(':')
+      env['CFLAGS'] = env_CFLAGS.join(' ')
+      env['LDFLAGS'] = env_LDFLAGS.join(' ')
+      env['LIBRARY_PATH'] = env_LIBRARY_PATH.join(':')
     end
 
     @compile_env = env