Fix TestAfdoDeps for darwin

LTO does not set the -import-instr-limit flag when building for
darwin, don't test it on darwin host modules.

Test: afdo_test.go
Change-Id: I83f77006a875f8b0a6af9ae11eb3bad88b0681b1
diff --git a/cc/afdo_test.go b/cc/afdo_test.go
index 3eab039..0679d13 100644
--- a/cc/afdo_test.go
+++ b/cc/afdo_test.go
@@ -15,6 +15,7 @@
 package cc
 
 import (
+	"runtime"
 	"strings"
 	"testing"
 
@@ -228,12 +229,14 @@
 			uniqueInternalLinkageNamesCFlag, cFlags)
 	}
 
-	ldFlags = libTestHost.Rule("ld").Args["ldFlags"]
-	if !strings.Contains(ldFlags, noAfdoLtoLdFlag) {
-		t.Errorf("Expected host 'libTest' to not enable afdo, but did not find %q in ldflags %q", noAfdoLtoLdFlag, ldFlags)
-	}
-	if strings.Contains(ldFlags, afdoLtoLdFlag) {
-		t.Errorf("Expected host 'libTest' to not enable afdo, but found %q in ldflags %q", afdoLtoLdFlag, ldFlags)
+	if runtime.GOOS != "darwin" {
+		ldFlags := libTestHost.Rule("ld").Args["ldFlags"]
+		if !strings.Contains(ldFlags, noAfdoLtoLdFlag) {
+			t.Errorf("Expected host 'libTest' to not enable afdo, but did not find %q in ldflags %q", noAfdoLtoLdFlag, ldFlags)
+		}
+		if strings.Contains(ldFlags, afdoLtoLdFlag) {
+			t.Errorf("Expected host 'libTest' to not enable afdo, but found %q in ldflags %q", afdoLtoLdFlag, ldFlags)
+		}
 	}
 
 	// Check dependency edge from afdo-enabled module to static deps