zig libc: allow non-native targets

On macos, allow targets supported by the SDK. This then spawns `xcrun`
and correct paths are emitted for:

- x86_64-macos
- x86_64-ios
- x86_64-tvos
- x86_64-watchos
- x86_64-ios-macbi
- aarch64-macos
- aarch64-ios
- aarch64-tvos
- aarch64-watchos
- aarch64-ios-macbi

On platforms with android NDK, allow android targets. Example usage:

```
CC=/NDK/.../bin/aarch64-linux-android34-clang zig libc -target aarch64-linux-android
```

lib/compiler/libc.zig

@@ -113,7 +113,7 @@ pub fn main() !void {
         };
         defer libc.deinit(gpa);
     } else {
-        if (!target_query.isNative()) {
+        if (!target_query.canDetectLibC()) {
             fatal("unable to detect libc for non-native target", .{});
         }
         var libc = LibCInstallation.findNative(.{

lib/std/Target/Query.zig

@@ -415,6 +415,15 @@ pub fn isNative(self: Query) bool {
     return self.isNativeCpu() and self.isNativeOs() and self.isNativeAbi();
 }
 
+pub fn canDetectLibC(self: Query) bool {
+    if (self.isNative()) return true;
+    if (self.os_tag) |os| {
+        if (builtin.os.tag == .macos and os.isDarwin()) return true;
+        if (os == .linux and self.abi == .android) return true;
+    }
+    return false;
+}
+
 /// Formats a version with the patch component omitted if it is zero,
 /// unlike SemanticVersion.format which formats all its version components regardless.
 fn formatVersion(version: SemanticVersion, writer: anytype) !void {

lib/std/zig/LibCInstallation.zig

@@ -167,7 +167,7 @@ pub const FindNativeOptions = struct {
 pub fn findNative(args: FindNativeOptions) FindError!LibCInstallation {
     var self: LibCInstallation = .{};
 
-    if (is_darwin) {
+    if (is_darwin and args.target.isDarwin()) {
         if (!std.zig.system.darwin.isSdkInstalled(args.allocator))
             return error.DarwinSdkNotFound;
         const sdk = std.zig.system.darwin.getSdk(args.allocator, args.target) orelse
@@ -196,7 +196,7 @@ pub fn findNative(args: FindNativeOptions) FindError!LibCInstallation {
         try self.findNativeCrtDirWindows(args, &sdk);
     } else if (is_haiku) {
         try self.findNativeIncludeDirPosix(args);
-        try self.findNativeCrtBeginDirHaiku(args);
+        try self.findNativeGccDirHaiku(args);
         self.crt_dir = try args.allocator.dupeZ(u8, "/system/develop/lib");
     } else if (builtin.target.os.tag.isSolarish()) {
         // There is only one libc, and its headers/libraries are always in the same spot.
@@ -443,13 +443,16 @@ fn findNativeCrtDirWindows(
 fn findNativeCrtDirPosix(self: *LibCInstallation, args: FindNativeOptions) FindError!void {
     self.crt_dir = try ccPrintFileName(.{
         .allocator = args.allocator,
-        .search_basename = "crt1.o",
+        .search_basename = switch (args.target.os.tag) {
+            .linux => if (args.target.isAndroid()) "crtbegin_dynamic.o" else "crt1.o",
+            else => "crt1.o",
+        },
         .want_dirname = .only_dir,
         .verbose = args.verbose,
     });
 }
 
-fn findNativeCrtBeginDirHaiku(self: *LibCInstallation, args: FindNativeOptions) FindError!void {
+fn findNativeGccDirHaiku(self: *LibCInstallation, args: FindNativeOptions) FindError!void {
     self.gcc_dir = try ccPrintFileName(.{
         .allocator = args.allocator,
         .search_basename = "crtbeginS.o",

lib/std/zig/system/darwin.zig

@@ -38,7 +38,11 @@ pub fn getSdk(allocator: Allocator, target: Target) ?[]const u8 {
     const is_simulator_abi = target.abi == .simulator;
     const sdk = switch (target.os.tag) {
         .macos => "macosx",
-        .ios => if (is_simulator_abi) "iphonesimulator" else "iphoneos",
+        .ios => switch (target.abi) {
+            .simulator => "iphonesimulator",
+            .macabi => "macosx",
+            else => "iphoneos",
+        },
         .watchos => if (is_simulator_abi) "watchsimulator" else "watchos",
         .tvos => if (is_simulator_abi) "appletvsimulator" else "appletvos",
         else => return null,