Remove PGO build support

We have removed our final PGO enabled project, time to remove PGO build
support.

Test: presubmit
Change-Id: I14ccd0fc8e3fbb8b3015072245fafd0eebe3ec08
diff --git a/cc/lto.go b/cc/lto.go
index 30d7b757..d2a43d2 100644
--- a/cc/lto.go
+++ b/cc/lto.go
@@ -140,7 +140,7 @@
 		// Reduce the inlining threshold for a better balance of binary size and
 		// performance.
 		if !ctx.Darwin() {
-			if ctx.isPgoCompile() || ctx.isAfdoCompile() {
+			if ctx.isAfdoCompile() {
 				ltoLdFlags = append(ltoLdFlags, "-Wl,-plugin-opt,-import-instr-limit=40")
 			} else {
 				ltoLdFlags = append(ltoLdFlags, "-Wl,-plugin-opt,-import-instr-limit=5")