Introduce skia_pic gyp variable.

gyp/common_conditions.gypi

Index: gyp/common_conditions.gypi
diff --git a/gyp/common_conditions.gypi b/gyp/common_conditions.gypi
index d03dfb00a6cea198a7a3e59d5f8814a29208fb01..51b44505b836071ec4545b0f462449314260cf51 100644
--- a/gyp/common_conditions.gypi
+++ b/gyp/common_conditions.gypi
@@ -8,6 +8,11 @@
     'SK_FORCE_DISTANCEFIELD_FONTS=<(skia_force_distancefield_fonts)',
   ],
   'conditions' : [
+    ['skia_pic', {
+     'cflags': [
+       '-fPIC',
+     ],
+    }],
     [ 'skia_arch_type == "arm64"', {
       'cflags': [
         '-ffp-contract=off',
@@ -403,9 +408,6 @@
         },
         'conditions' : [
           [ 'skia_shared_lib', {
-            'cflags': [
-              '-fPIC',
-            ],
             'defines': [
               'SKIA_DLL',
               'SKIA_IMPLEMENTATION=1',
@@ -449,7 +451,6 @@
             'conditions' : [
               [ 'skia_sanitizer == "thread"', {
                 'defines': [ 'SK_DYNAMIC_ANNOTATIONS_ENABLED=1' ],
-                'cflags': [ '-fPIC' ],
                 'target_conditions': [
                   [ '_type == "executable"', {

[mtklein, 2014/07/19 14:49:19]

Can we make skia_pic imply PIE executables too, or is that somehow now required
for Android?

I guess it's moot if we're always deploying as shared_libraries on our Android
bots?

[djsollen, 2014/07/22 14:20:17]

We need PIE for android executables as well.  The only android executable is
currently skia_launcher and it explicitly sets that in the gyp.

[scroggo, 2014/07/22 14:53:36]

(Derek and I discussed in person, but for posterity:)
Moving this into skia_pic breaks Android. Our Android build currently does
something sneaky: our tools (e.g. SampleApp) use the type 'executable', but then
we change its type to 'shared_library' after the fact (see
platform_tools/android/gyp/dependencies.gyp). Then skia_launcher includes that
shared library. When I run android_ninja, SampleApp is considered an executable
(I'm guessing gyp reaches here before reaching the gyp file to change the type),
so it complains that executable is lacking a function main.

I can think of a few solutions:
- Don't define skia_pic for Android (downside here is that if someone *does*
  define it locally, they won't build)
- Don't include this as part of skia_pic (reduces code sharing)
- Change the way the executables get turned into shared libraries on Android
  (the current approach has a comment that it is designed to increase code
  sharing, but perhaps we can come up with another solution that does not
  reduce it).
- Skip the skia_launcher, and actually build the executables as executables
  (I'm sure there is a good reason for using skia_launcher though)
- Skip this part on Android (Derek actually proposed this, and it's probably
  the simplest approach.)

Thoughts?

                     'cflags': [ '-fPIE' ],
@@ -458,7 +459,6 @@
                 ],
               }],
               [ 'skia_sanitizer == "undefined"', {
-                'cflags': [ '-fPIC' ],
                 'cflags_cc!': ['-fno-rtti'],
                 'target_conditions': [
                   [ '_type == "executable"', {
@@ -664,9 +664,6 @@
             ],
           }],
           [ 'skia_shared_lib', {
-            'cflags': [
-              '-fPIC',
-            ],
             'defines': [
               'SKIA_DLL',
               'SKIA_IMPLEMENTATION=1',