Add the possibility to build with PGO when using Clang

chrome/test/data/nacl/BUILD.gn

Index: chrome/test/data/nacl/BUILD.gn
diff --git a/chrome/test/data/nacl/BUILD.gn b/chrome/test/data/nacl/BUILD.gn
index 64e5d25b7b6e506f372f374d9291ba946ec6f188..ce538345631f35b79764a1c3aa8ab46114829e5e 100644
--- a/chrome/test/data/nacl/BUILD.gn
+++ b/chrome/test/data/nacl/BUILD.gn
@@ -602,6 +602,9 @@ if (is_linux && is_clang) {
     defines = [ "NACL_LINUX=1" ]
     include_dirs = [ "../../../.." ]
 
+    # Do not use PGO, which requires a few symbols.
+    configs -= [ "//build/config/pgo:default_pgo_flags" ]

[Sébastien Marchand, 2016/11/17 17:31:15]

Again, I'll do the opposite, include it when you need it.

+
     # Do not use any sanitizers tools, which require a few symbols.
     configs -= [ "//build/config/sanitizers:default_sanitizer_flags" ]
     configs += [ ":nonsfi_libc_free_nexe_config" ]