Make improvements

- Introduce portable sched_getcpu() api
- Support GCC's __target_clones__ feature
- Make fma() go faster on x86 in default mode
- Remove some asan checks from core libraries
- WinMain() now ensures $HOME and $USER are defined

libc/stdio/ftw.c

@@ -50,5 +50,5 @@ int ftw(const char *dirpath,
 	/* The following cast assumes that calling a function with one
 	 * argument more than it needs behaves as expected. This is
 	 * actually undefined, but works on all real-world machines. */
-	return nftw(dirpath, (int (*)())fn, fd_limit, FTW_PHYS);
+	return nftw(dirpath, (void *)fn, fd_limit, FTW_PHYS);
 }