Remove libgcc toolchain libs for Android

Remove Android-targeting gcc toolchain libraries -- libgcc,
libgcc_stripped, libatomic, and libgcov. Also remove libunwind_llvm,
which is replaced with a libunwind toolchain prebuilt.

The __atomic_* library functions are now part of the compiler-rt
builtins library:

https://android-review.googlesource.com/c/toolchain/llvm_android/+/1625025

Bug: http://b/153025717
Test: treehugger
Change-Id: I971d0a4a49f1aaeb3546e80b6d94208277a171ac

cc/cc_test.go

@@ -2912,13 +2912,13 @@ func TestStaticLibDepExport(t *testing.T) {
 	// Check the shared version of lib2.
 	variant := "android_arm64_armv8-a_shared"
 	module := ctx.ModuleForTests("lib2", variant).Module().(*Module)
-	checkStaticLibs(t, []string{"lib1", "libc++demangle", "libclang_rt.builtins-aarch64-android", "libatomic"}, module)
+	checkStaticLibs(t, []string{"lib1", "libc++demangle", "libclang_rt.builtins-aarch64-android"}, module)
 
 	// Check the static version of lib2.
 	variant = "android_arm64_armv8-a_static"
 	module = ctx.ModuleForTests("lib2", variant).Module().(*Module)
 	// libc++_static is linked additionally.
-	checkStaticLibs(t, []string{"lib1", "libc++_static", "libc++demangle", "libclang_rt.builtins-aarch64-android", "libatomic"}, module)
+	checkStaticLibs(t, []string{"lib1", "libc++_static", "libc++demangle", "libclang_rt.builtins-aarch64-android"}, module)
 }
 
 var compilerFlagsTestCases = []struct {

cc/linker.go

@@ -321,10 +321,9 @@ func (linker *baseLinker) linkerDeps(ctx DepsContext, deps Deps) Deps {
 	}
 
 	if ctx.toolchain().Bionic() {
-		// libclang_rt.builtins and libatomic have to be last on the command line
+		// libclang_rt.builtins has to be last on the command line
 		if !Bool(linker.Properties.No_libcrt) {
 			deps.LateStaticLibs = append(deps.LateStaticLibs, config.BuiltinsRuntimeLibrary(ctx.toolchain()))
-			deps.LateStaticLibs = append(deps.LateStaticLibs, "libatomic")
 		}
 
 		deps.SystemSharedLibs = linker.Properties.System_shared_libs

cc/testing.go

@@ -62,17 +62,6 @@ func GatherRequiredDepsForTest(oses ...android.OsType) string {
 
 func commonDefaultModules() string {
 	return `
-		toolchain_library {
-			name: "libatomic",
-			defaults: ["linux_bionic_supported"],
-			vendor_available: true,
-			vendor_ramdisk_available: true,
-			product_available: true,
-			recovery_available: true,
-			native_bridge_supported: true,
-			src: "",
-		}
-
 		toolchain_library {
 			name: "libcompiler_rt-extras",
 			vendor_available: true,
@@ -200,29 +189,6 @@ func commonDefaultModules() string {
 			srcs: [""],
 		}
 
-		toolchain_library {
-			name: "libgcc",
-			defaults: ["linux_bionic_supported"],
-			vendor_available: true,
-			product_available: true,
-			recovery_available: true,
-			src: "",
-			apex_available: [
-				"//apex_available:platform",
-				"//apex_available:anyapex",
-			],
-		}
-
-		toolchain_library {
-			name: "libgcc_stripped",
-			defaults: ["linux_bionic_supported"],
-			vendor_available: true,
-			product_available: true,
-			recovery_available: true,
-			sdk_version: "current",
-			src: "",
-		}
-
 		cc_library {
 			name: "libc",
 			defaults: ["linux_bionic_supported"],
@@ -398,16 +364,6 @@ func commonDefaultModules() string {
 				"//apex_available:anyapex",
 			],
 		}
-		cc_library {
-			name: "libunwind_llvm",
-			no_libcrt: true,
-			nocrt: true,
-			system_shared_libs: [],
-			stl: "none",
-			vendor_available: true,
-			product_available: true,
-			recovery_available: true,
-		}
 
 		cc_defaults {
 			name: "crt_defaults",