POSIX: Implement the fastbuild option.

BUG=none
TEST=Enabling fastbuild -> faster debug build.
Review URL: http://codereview.chromium.org/1558043

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@44543 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/build/common.gypi b/build/common.gypi
index 29ccfbe..33a24b3 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -379,7 +379,9 @@
                 'DebugInformationFormat': '0',
               }
             }
-         }],  # OS==win
+          }, { # else: OS != "win"
+            'cflags': [ '-g1' ],
+          }],
         ],  # conditions for fastbuild.
       }],  # fastbuild!=0
       ['selinux==1', {