internal/buildcfg: enable greenteagc experiment for loong64

The loong64 compiler bug has been resolved, so we can now
unconditionally enable the experiment on the architecture.

Updates #73581
Fixes #75776

Change-Id: I390f8a125d43ca64798ea5b6a408aaf7220fadbf
Reviewed-on: https://go-review.googlesource.com/c/go/+/710476
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Auto-Submit: abner chenc <chenguoqi@loongson.cn>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: abner chenc <chenguoqi@loongson.cn>
Reviewed-by: Cherry Mui <cherryyz@google.com>

src/internal/buildcfg/exp.go

@@ -78,18 +78,13 @@ func ParseGOEXPERIMENT(goos, goarch, goexp string) (*ExperimentFlags, error) {
 	// things like .debug_addr (needed for DWARF 5).
 	dwarf5Supported := (goos != "darwin" && goos != "ios" && goos != "aix")
 
-	// The compiler crashes while compiling some of the Green Tea code.
-	// The Green Tea code is pretty normal, so this is likely a compiler
-	// bug in the loong64 port.
-	greenTeaGCSupported := goarch != "loong64"
-
 	baseline := goexperiment.Flags{
 		RegabiWrappers:        regabiSupported,
 		RegabiArgs:            regabiSupported,
 		Dwarf5:                dwarf5Supported,
 		RandomizedHeapBase64:  true,
 		SizeSpecializedMalloc: true,
-		GreenTeaGC:            greenTeaGCSupported,
+		GreenTeaGC:            true,
 	}
 
 	// Start with the statically enabled set of experiments.