Don't pass -lrt or -lgcc_s to darwin rust compiles

Fix mac builds by removing the -lrt and -lgcc_s flags from darwin
rust compiles.

Bug: 293349612
Test: builds
Change-Id: I99a9fea963761730efc4d3236135ee6d83dbca57
diff --git a/rust/compiler.go b/rust/compiler.go
index 6f61798..98a61af 100644
--- a/rust/compiler.go
+++ b/rust/compiler.go
@@ -327,9 +327,9 @@
 		flags.LinkFlags = append(flags.LinkFlags, cc.RpathFlags(ctx)...)
 	}
 
-	if !ctx.toolchain().Bionic() && ctx.Os() != android.LinuxMusl && !ctx.Windows() {
-		// Add -lc, -lrt, -ldl, -lpthread, -lm, -lrt and -lgcc_s to host builds to match the default behavior of device
-		// builds. This is irrelevant for the Windows target as these are Posix specific.
+	if ctx.Os() == android.Linux {
+		// Add -lc, -lrt, -ldl, -lpthread, -lm and -lgcc_s to glibc builds to match
+		// the default behavior of device builds.
 		flags.LinkFlags = append(flags.LinkFlags,
 			"-lc",
 			"-lrt",
@@ -338,6 +338,15 @@
 			"-lm",
 			"-lgcc_s",
 		)
+	} else if ctx.Os() == android.Darwin {
+		// Add -lc, -ldl, -lpthread and -lm to glibc darwin builds to match the default
+		// behavior of device builds.
+		flags.LinkFlags = append(flags.LinkFlags,
+			"-lc",
+			"-ldl",
+			"-lpthread",
+			"-lm",
+		)
 	}
 	return flags
 }