GN: support compiler_prefix, use it for ccache on bots.

This makes it considerably easier to use ccache with the Android NDK.
You can now just set
  compiler_prefix = "ccache"
  ndk = "/path/to/ndk"
and we'll use the NDK clang, wrapped with ccache.

The name compiler_prefix is stolen from / compatible with Chrome.

If you have ccache, you can just always leave compiler_prefix="ccache" enabled.
This should make it an unusual thing for humans to have to change cc or cxx.

GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2281163002

Review-Url: https://codereview.chromium.org/2281163002

6 files changed, 8 insertions, 6 deletions

diff --git a/infra/bots/recipe_modules/flavor/gn_flavor.py b/infra/bots/recipe_modules/flavor/gn_flavor.py
index 75c318f818..cba72a8467 100644
--- a/infra/bots/recipe_modules/flavor/gn_flavor.py
+++ b/infra/bots/recipe_modules/flavor/gn_flavor.py
@@ -29,9 +29,10 @@ class GNFlavorUtils(default_flavor.DefaultFlavorUtils):
     elif compiler == 'GCC':
       cc, cxx = 'gcc', 'g++'
 
+    compiler_prefix = ""
     ccache = self.m.run.ccache()
     if ccache:
-      cc, cxx = '%s %s' % (ccache, cc), '%s %s' % (ccache, cxx)
+      compiler_prefix = ccache
       if compiler == 'Clang':
         # Stifle "argument unused during compilation: ..." warnings.
         extra_cflags.append('-Qunused-arguments')
@@ -45,6 +46,7 @@ class GNFlavorUtils(default_flavor.DefaultFlavorUtils):
     gn_args = ' '.join('%s=%s' % (k,v) for (k,v) in {
         'cc': quote(cc),
         'cxx': quote(cxx),
+        'compiler_prefix': quote(compiler_prefix),
         'extra_cflags': quote(' '.join(extra_cflags)),
         'is_debug': 'true' if configuration == 'Debug' else 'false',
     }.iteritems())
diff --git a/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-Clang-x86_64-Debug-GN.json b/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-Clang-x86_64-Debug-GN.json
index 3e3ef0e0bd..35c21ce889 100644
--- a/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-Clang-x86_64-Debug-GN.json
+++ b/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-Clang-x86_64-Debug-GN.json
@@ -127,7 +127,7 @@
       "gn",
       "gen",
       "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-Clang-x86_64-Debug-GN/Debug",
-      "--args=cc=\"/usr/bin/ccache clang\" cxx=\"/usr/bin/ccache clang++\" is_debug=true extra_cflags=\"-Qunused-arguments\""
+      "--args=cc=\"clang\" cxx=\"clang++\" is_debug=true extra_cflags=\"-Qunused-arguments\" compiler_prefix=\"/usr/bin/ccache\""
     ],
     "cwd": "[CUSTOM_/_B_WORK]/skia",
     "env": {
diff --git a/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-GCC-x86_64-Debug-GN.json b/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-GCC-x86_64-Debug-GN.json
index 10ff8c3307..253f918399 100644
--- a/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-GCC-x86_64-Debug-GN.json
+++ b/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-GCC-x86_64-Debug-GN.json
@@ -125,7 +125,7 @@
       "gn",
       "gen",
       "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86_64-Debug-GN/Debug",
-      "--args=cc=\"/usr/bin/ccache gcc\" cxx=\"/usr/bin/ccache g++\" is_debug=true extra_cflags=\"\""
+      "--args=cc=\"gcc\" cxx=\"g++\" is_debug=true extra_cflags=\"\" compiler_prefix=\"/usr/bin/ccache\""
     ],
     "cwd": "[CUSTOM_/_B_WORK]/skia",
     "env": {
diff --git a/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-GCC-x86_64-Debug-SK_USE_DISCARDABLE_SCALEDIMAGECACHE.json b/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-GCC-x86_64-Debug-SK_USE_DISCARDABLE_SCALEDIMAGECACHE.json
index 12314f87cc..090d312016 100644
--- a/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-GCC-x86_64-Debug-SK_USE_DISCARDABLE_SCALEDIMAGECACHE.json
+++ b/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-GCC-x86_64-Debug-SK_USE_DISCARDABLE_SCALEDIMAGECACHE.json
@@ -124,7 +124,7 @@
       "gn",
       "gen",
       "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86_64-Debug-SK_USE_DISCARDABLE_SCALEDIMAGECACHE/Debug",
-      "--args=cc=\"gcc\" cxx=\"g++\" is_debug=true extra_cflags=\"-DSK_USE_DISCARDABLE_SCALEDIMAGECACHE\""
+      "--args=cc=\"gcc\" cxx=\"g++\" is_debug=true extra_cflags=\"-DSK_USE_DISCARDABLE_SCALEDIMAGECACHE\" compiler_prefix=\"\""
     ],
     "cwd": "[CUSTOM_/_B_WORK]/skia",
     "env": {
diff --git a/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-GCC-x86_64-Release-Fast.json b/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-GCC-x86_64-Release-Fast.json
index 091b29ebb1..10321f6f9a 100644
--- a/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-GCC-x86_64-Release-Fast.json
+++ b/infra/bots/recipes/swarm_compile.expected/Build-Ubuntu-GCC-x86_64-Release-Fast.json
@@ -123,7 +123,7 @@
       "gn",
       "gen",
       "[CUSTOM_/_B_WORK]/skia/out/Build-Ubuntu-GCC-x86_64-Release-Fast/Release",
-      "--args=cc=\"gcc\" cxx=\"g++\" is_debug=false extra_cflags=\"-march=native -fomit-frame-pointer -O3\""
+      "--args=cc=\"gcc\" cxx=\"g++\" is_debug=false extra_cflags=\"-march=native -fomit-frame-pointer -O3\" compiler_prefix=\"\""
     ],
     "cwd": "[CUSTOM_/_B_WORK]/skia",
     "env": {
diff --git a/infra/bots/recipes/swarm_compile.expected/Build-Win-MSVC-x86-Release-GN.json b/infra/bots/recipes/swarm_compile.expected/Build-Win-MSVC-x86-Release-GN.json
index fe8c242369..62b59e92c8 100644
--- a/infra/bots/recipes/swarm_compile.expected/Build-Win-MSVC-x86-Release-GN.json
+++ b/infra/bots/recipes/swarm_compile.expected/Build-Win-MSVC-x86-Release-GN.json
@@ -93,7 +93,7 @@
       "gn",
       "gen",
       "[CUSTOM_C:\\_B_WORK]\\skia\\out\\Build-Win-MSVC-x86-Release-GN\\Release",
-      "--args=cc=\"cc\" cxx=\"c++\" is_debug=false extra_cflags=\"\""
+      "--args=cc=\"cc\" cxx=\"c++\" is_debug=false extra_cflags=\"\" compiler_prefix=\"\""
     ],
     "cwd": "[CUSTOM_C:\\_B_WORK]\\skia",
     "env": {