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

third_party/chibicc/test/test.mk

@@ -79,7 +79,7 @@ o/$(MODE)/third_party/chibicc/test/%.com.dbg:					\
 		o/$(MODE)/third_party/chibicc/test/%.chibicc.o			\
 		$(THIRD_PARTY_CHIBICC_TEST_A).pkg				\
 		$(CRT)								\
-		$(APE)
+		$(APE_NO_MODIFY_SELF)
 	@$(APELINK)
 
 o/$(MODE)/third_party/chibicc/test/%2.com.dbg:					\
@@ -88,7 +88,7 @@ o/$(MODE)/third_party/chibicc/test/%2.com.dbg:					\
 		o/$(MODE)/third_party/chibicc/test/%.chibicc2.o			\
 		$(THIRD_PARTY_CHIBICC_TEST2_A).pkg				\
 		$(CRT)								\
-		$(APE)
+		$(APE_NO_MODIFY_SELF)
 	@$(APELINK)
 
 .PRECIOUS: $(THIRD_PARTY_CHIBICC_TEST_OBJS)