Add the possibility to build with PGO when using Clang

build/config/compiler/compiler.gni

Index: build/config/compiler/compiler.gni
diff --git a/build/config/compiler/compiler.gni b/build/config/compiler/compiler.gni
index e88318f88a763ef64b43d60df73aa4f112d8660f..df12be920b53319190d9b60bb0994165e2000d43 100644
--- a/build/config/compiler/compiler.gni
+++ b/build/config/compiler/compiler.gni
@@ -5,6 +5,7 @@
 import("//build/config/android/config.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
+import("//build/config/compiler/pgo/pgo.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/toolchain/goma.gni")
 import("//build/toolchain/toolchain.gni")
@@ -40,15 +41,6 @@ declare_args() {
   # can be used to convert a fastlink pdb to a normal one.
   is_win_fastlink = false
 
-  # Specify the current PGO phase, only used for the Windows MSVS build. Here's
-  # the different values that can be used:
-  #     0 : Means that PGO is turned off.
-  #     1 : Used during the PGI (instrumentation) phase.
-  #     2 : Used during the PGO (optimization) phase.
-  #
-  # TODO(sebmarchand): Add support for the PGU (update) phase.
-  chrome_pgo_phase = 0
-
   # Whether or not we should turn on incremental WPO. Only affects the VS
   # Windows build.
   use_incremental_wpo = false