feat(libzigc): add common implementations of pthread_spin_*

* and remove their mingw, musl and wasi implementations

test/c.zig

@@ -4,6 +4,7 @@ const std = @import("std");
 test {
     _ = @import("c/inttypes.zig");
     _ = @import("c/math.zig");
+    _ = @import("c/pthread.zig");
     _ = @import("c/search.zig");
     _ = @import("c/stdlib.zig");
     _ = @import("c/string.zig");

test/c/pthread.zig

@@ -0,0 +1,20 @@
+const builtin = @import("builtin");
+const std = @import("std");
+
+const c = std.c;
+const math = std.math;
+const testing = std.testing;
+
+test "pthread_spinlock_t" {
+    if (builtin.target.os.tag.isDarwin()) return; // Darwin doesn't have `pthread_spin_*`
+
+    var spin: c.pthread_spinlock_t = undefined;
+    _ = c.pthread_spin_init(&spin, c.PTHREAD_PROCESS_PRIVATE);
+    defer _ = c.pthread_spin_destroy(&spin);
+
+    try std.testing.expectEqual(.SUCCESS, c.pthread_spin_trylock(&spin));
+    try std.testing.expectEqual(.SUCCESS, c.pthread_spin_unlock(&spin));
+
+    try std.testing.expectEqual(.SUCCESS, c.pthread_spin_lock(&spin));
+    try std.testing.expectEqual(.SUCCESS, c.pthread_spin_unlock(&spin));
+}