Toolchain: Don't pass -lpthread when pthreads are requested

This is essentially a no-op since we have our replacement linker script,
but if we can skip over that entirely, why not?

Toolchain/Patches/gcc/0001-Add-a-gcc-driver-for-SerenityOS.patch

@@ -96,7 +96,7 @@ index 000000000..dc2f5361e
 +/* Default arguments you want when running your
 +   i686-serenity-gcc/x86_64-serenity-gcc toolchain */
 +#undef LIB_SPEC
-+#define LIB_SPEC "%{pthread:-lpthread} -lc" /* link against C standard library */
++#define LIB_SPEC "-lc" /* link against C standard library */
 +
 +/* Files that are linked before user code.
 +   The %s tells GCC to look for these files in the library directory. */

Toolchain/Patches/llvm/0003-Driver-Add-support-for-SerenityOS.patch

@@ -144,7 +144,7 @@ new file mode 100644
 index 000000000..955422438
 --- /dev/null
 +++ b/clang/lib/Driver/ToolChains/Serenity.cpp
-@@ -0,0 +1,340 @@
+@@ -0,0 +1,337 @@
 +//===---- Serenity.cpp - SerenityOS ToolChain Implementation ----*- C++ -*-===//
 +//
 +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
@@ -306,9 +306,6 @@ index 000000000..955422438
 +  }
 +
 +  if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
-+    if (Args.hasArg(options::OPT_pthread, options::OPT_pthreads))
-+      CmdArgs.push_back("-lpthread");
-+
 +    if (!Args.hasArg(options::OPT_nolibc))
 +      CmdArgs.push_back("-lc");
 +  }