Make build hermetic without shell scripts

- Fix some minor issues in ar.com
- Have execve() look for `ape` command
- Rewrite NT paths using /c/ rather /??/c:/
- Replace broken GCC symlinks with .sym files
- Rewrite $PATH environment variables on startup
- Make $(APE_NO_MODIFY_SELF) the default bootloader
- Add all build command dependencies to build/bootstrap
- Get the repository mostly building from source on non-Linux

test/libc/calls/clock_gettime_test.c

@@ -35,7 +35,7 @@ TEST(clock_gettime, test) {
   ASSERT_NE(0, ts.tv_sec);
   ASSERT_NE(0, ts.tv_nsec);
   if (__is_linux_2_6_23()) {
-    ASSERT_GT((intptr_t)__get_clock_gettime(&isfast),
+    ASSERT_GT((intptr_t)__clock_gettime_get(&isfast),
               getauxval(AT_SYSINFO_EHDR));
     ASSERT_TRUE(isfast);
   }