Link without crtbegin.o and crtend.o on Linux when the C compiler has none, as
with clang and compiler-rt and no GCC, as Zig 0.16 did.

--- a/lib/std/zig/LibCInstallation.zig
+++ b/lib/std/zig/LibCInstallation.zig
@@ -104,7 +104,7 @@
 
     const os_tag = target.os.tag;
 
-    if (self.cc_dir == null and (os_tag == .haiku or os_tag == .serenity or os_tag == .linux)) {
+    if (self.cc_dir == null and (os_tag == .haiku or os_tag == .serenity)) {
         log.err("cc_dir may not be empty for {s}", .{@tagName(os_tag)});
         return error.ParseError;
     }
@@ -229,7 +229,12 @@
             .freebsd, .netbsd, .openbsd, .dragonfly => self.crt_dir = try gpa.dupe(u8, "/usr/lib"),
             .linux => {
                 try self.findNativeCrtDirPosix(gpa, io, args);
-                try self.findNativeGccDirPosix(gpa, io, args);
+                // A toolchain without GCC, such as clang with compiler-rt, has
+                // no crtbegin.o; link without it as before.
+                self.findNativeGccDirPosix(gpa, io, args) catch |err| switch (err) {
+                    error.LibCRuntimeNotFound => {},
+                    else => |e| return e,
+                };
             },
             else => {},
         }
@@ -1032,15 +1037,15 @@
             };
         },
         .haiku, .serenity, .linux => {
-            const cc_dir_path: Path = .{
+            const cc_dir_path: ?Path = if (lci.cc_dir) |cc_dir| .{
                 .root_dir = Cache.Directory.cwd(),
-                .sub_path = lci.cc_dir orelse return error.LibCInstallationMissingCcDir,
-            };
+                .sub_path = cc_dir,
+            } else if (target.os.tag == .linux) null else return error.LibCInstallationMissingCcDir;
             return .{
                 .crt0 = if (crt_basenames.crt0) |basename| try crt_dir_path.join(arena, basename) else null,
                 .crti = if (crt_basenames.crti) |basename| try crt_dir_path.join(arena, basename) else null,
-                .crtbegin = if (crt_basenames.crtbegin) |basename| try cc_dir_path.join(arena, basename) else null,
-                .crtend = if (crt_basenames.crtend) |basename| try cc_dir_path.join(arena, basename) else null,
+                .crtbegin = if (cc_dir_path) |p| if (crt_basenames.crtbegin) |basename| try p.join(arena, basename) else null else null,
+                .crtend = if (cc_dir_path) |p| if (crt_basenames.crtend) |basename| try p.join(arena, basename) else null else null,
                 .crtn = if (crt_basenames.crtn) |basename| try crt_dir_path.join(arena, basename) else null,
             };
         },