Meta: Add ccache compiler launcher to gn build

Author: https://github.com/ADKaster
Commit: https://github.com/SerenityOS/serenity/commit/863fad0e32
Pull-request: https://github.com/SerenityOS/serenity/pull/20209

Meta/gn/build/toolchain/BUILD.gn

@@ -21,6 +21,9 @@ template("unix_toolchain") {
                ])
 
     tool("cc") {
+      if (enable_ccache) {
+        command_launcher = "ccache"
+      }
       depfile = "{{output}}.d"
       command = "$cc -MMD -MF $depfile -o {{output}} -c {{source}} {{defines}} {{include_dirs}} {{cflags}} {{cflags_c}}"
       depsformat = "gcc"
@@ -29,6 +32,9 @@ template("unix_toolchain") {
     }
 
     tool("cxx") {
+      if (enable_ccache) {
+        command_launcher = "ccache"
+      }
       depfile = "{{output}}.d"
       command = "$cxx -MMD -MF $depfile -o {{output}} -c {{source}} {{defines}} {{include_dirs}} {{cflags}} {{cflags_cc}}"
       depsformat = "gcc"
@@ -37,6 +43,9 @@ template("unix_toolchain") {
     }
 
     tool("objcxx") {
+      if (enable_ccache) {
+        command_launcher = "ccache"
+      }
       depfile = "{{output}}.d"
       command = "$cxx -MMD -MF $depfile -o {{output}} -c {{source}} {{defines}} {{include_dirs}} {{cflags}} {{cflags_objcc}}"
       depsformat = "gcc"
@@ -45,6 +54,9 @@ template("unix_toolchain") {
     }
 
     tool("asm") {
+      if (enable_ccache) {
+        command_launcher = "ccache"
+      }
       depfile = "{{output}}.d"
       command = "$cc -MMD -MF $depfile -o {{output}} -c {{source}} {{defines}} {{include_dirs}} {{asmflags}}"
       depsformat = "gcc"
@@ -53,6 +65,9 @@ template("unix_toolchain") {
     }
 
     tool("alink") {
+      if (enable_ccache) {
+        command_launcher = "ccache"
+      }
       if (current_os == "ios" || current_os == "mac") {
         command = "libtool -D -static -no_warning_for_no_symbols {{arflags}} -o {{output}} {{inputs}}"
         not_needed([ "ar" ])
@@ -78,6 +93,9 @@ template("unix_toolchain") {
     lib_dir_switch = "-L"
 
     tool("solink") {
+      if (enable_ccache) {
+        command_launcher = "ccache"
+      }
       outfile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"
       if (current_os == "ios" || current_os == "mac") {
         command = "$ld -shared {{ldflags}} -o $outfile {{inputs}} {{libs}} {{frameworks}} -Wl,-install_name,@rpath/{{target_output_name}}{{output_extension}}"
@@ -98,6 +116,9 @@ template("unix_toolchain") {
     }
 
     tool("solink_module") {
+      if (enable_ccache) {
+        command_launcher = "ccache"
+      }
       outfile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"
       if (current_os == "ios" || current_os == "mac") {
         command = "$ld -shared {{ldflags}} -Wl,-flat_namespace -Wl,-undefined,suppress -o $outfile {{inputs}} {{libs}} {{frameworks}} -Wl,-install_name,@rpath/{{target_output_name}}{{output_extension}}"
@@ -117,6 +138,9 @@ template("unix_toolchain") {
     }
 
     tool("link") {
+      if (enable_ccache) {
+        command_launcher = "ccache"
+      }
       outfile = "{{output_dir}}/{{target_output_name}}{{output_extension}}"
       if (current_os == "ios" || current_os == "mac") {
         command = "$ld {{ldflags}} -o $outfile {{inputs}} {{libs}} {{frameworks}} -Wl,-rpath,@executable_path/../lib"

Meta/gn/build/toolchain/compiler.gni

@@ -5,4 +5,7 @@ declare_args() {
   # Enable setting -fuse-ld and other flags for using the lld linker.
   # Should not be set on macOS when using the default system compiler.
   use_lld = false
+
+  # Use ccache as a compiler launcher for compile and link jobs
+  enable_ccache = true
 }