Revert 121165 - Revert 121068 - linux: add a use_gold flag that defaults to on

[This CL was backed out speculatively due to failures on the cros trunk bot. But this CL
was not the cause of that problem, so I'm un-doing the revert.]

Currently, gyp attempts to autodetect whether the linker supports
the --icf flag.  It's more predictable to just require the caller
to specify whether they're using gold.

As a first demonstration of this, drop LINKER_USES_ICF code in the
Chrome build.  (I'll follow up with a gyp patch to remove the
LINKER_USES_ICF stuff in gyp.)

Review URL: https://chromiumcodereview.appspot.com/9368015

TBR=evan@chromium.org
Review URL: https://chromiumcodereview.appspot.com/9372012

git-svn-id: http://src.chromium.org/svn/trunk/src/build@121175 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -387,12 +387,16 @@
           'enable_plugin_installation%': 1,
         }],
 
-        # Set to 0 to not use third_party/gold as the linker.
+        # linux_use_gold_binary: whether to use the binary checked into
+        # third_party/gold.
+        # linux_use_gold_flags: whether to use build flags that rely on gold.
         # On by default for x64 Linux.
         ['host_arch=="x64"', {
           'linux_use_gold_binary%': 1,
+          'linux_use_gold_flags%': 1,
         }, {
           'linux_use_gold_binary%': 0,
+          'linux_use_gold_flags%': 0,
         }],
 
         # Enable canvas_skia_skia.cc incrementally on different platforms.
@@ -460,6 +464,7 @@
     'enable_web_intents_tag%': '<(enable_web_intents_tag)',
     'enable_plugin_installation%': '<(enable_plugin_installation)',
     'linux_use_gold_binary%': '<(linux_use_gold_binary)',
+    'linux_use_gold_flags%': '<(linux_use_gold_flags)',
     'use_canvas_skia_skia%': '<(use_canvas_skia_skia)',
     # Whether to build for Wayland display server
     'use_wayland%': 0,
@@ -631,6 +636,8 @@
     # whether warnings are treated as errors.
     'chromium_code%': 0,
 
+    'release_valgrind_build%': 0,
+
     # TODO(thakis): Make this a blacklist instead, http://crbug.com/101600
     'enable_wexit_time_destructors%': 0,
 
@@ -1002,7 +1009,8 @@
 
       'release_extra_cflags%': '',
       'debug_extra_cflags%': '',
-      'release_valgrind_build%': 0,
+
+      'release_valgrind_build%': '<(release_valgrind_build)',
 
       # the non-qualified versions are widely assumed to be *nix-only
       'win_release_extra_cflags%': '',
@@ -1725,23 +1733,7 @@
                   '-g',
                 ],
               }],
-              # At gyp time, we test the linker for ICF support; this flag
-              # is then provided to us by gyp.  (Currently only gold supports
-              # an --icf flag.)
-              # There seems to be a conflict of --icf and -pie in gold which
-              # can generate crashy binaries. As a security measure, -pie
-              # takes precendence for now.
-              ['LINKER_SUPPORTS_ICF==1 and release_valgrind_build==0', {
-                'target_conditions': [
-                  ['_toolset=="target"', {
-                    'ldflags': [
-                      #'-Wl,--icf=safe',
-                      '-Wl,--icf=none',
-                    ]
-                  }]
-                ]
-              }],
-            ]
+            ],
           },
         },
         'variants': {
@@ -2007,6 +1999,24 @@
             'defines': ['KEEP_SHADOW_STACKS'],
             'cflags': ['-finstrument-functions'],
           }],
+          ['linux_use_gold_flags==1', {
+            'conditions': [
+              ['release_valgrind_build==0', {
+                'target_conditions': [
+                  ['_toolset=="target"', {
+                    'ldflags': [
+                      # There seems to be a conflict of --icf and -pie
+                      # in gold which can generate crashy binaries. As
+                      # a security measure, -pie takes precendence for
+                      # now.
+                      #'-Wl,--icf=safe',
+                      '-Wl,--icf=none',
+                    ],
+                  }],
+                ],
+              }],
+            ],
+          }],
           ['linux_use_gold_binary==1', {
             'variables': {
               # We pass the path to gold to the compiler.  gyp leaves