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

tool/decode/zip.c

@@ -57,7 +57,6 @@ dontdiscard char *FormatDosTime(uint16_t dostime) {
 }
 
 void AdvancePosition(uint8_t *map, size_t *pos, size_t off) {
-  CHECK_GE(off, *pos);
   if (off > *pos) {
     printf("\n/\t<%s>\n", "LIMBO");
     disassemblehex(&map[*pos], off - *pos, stdout);