Clean up more code

- Found some bugs in LLVM compiler-rt library
- The useless LIBC_STUBS package is now deleted
- Improve the overflow checking story even further
- Get chibicc tests working in MODE=dbg mode again
- The libc/isystem/ headers now have correctly named guards

libc/vga/tty.greg.c

@@ -1002,7 +1002,7 @@ static void TtySelectGraphicsRendition(struct Tty *tty) {
             tty->pr &= ~kTtyTrue;
             break;
           default:
-            abort();
+            __builtin_trap();
         }
         break;
       default:

libc/vga/vga.mk

@@ -27,12 +27,11 @@ LIBC_VGA_A_CHECKS =					\
 	$(LIBC_VGA_A_HDRS:%=o/$(MODE)/%.ok)
 
 LIBC_VGA_A_DIRECTDEPS =					\
-	LIBC_NEXGEN32E					\
-	LIBC_SYSV					\
-	LIBC_STR					\
+	LIBC_FMT					\
 	LIBC_INTRIN					\
-	LIBC_STUBS					\
-	LIBC_FMT
+	LIBC_NEXGEN32E					\
+	LIBC_STR					\
+	LIBC_SYSV
 
 LIBC_VGA_A_DEPS :=					\
 	$(call uniq,$(foreach x,$(LIBC_VGA_A_DIRECTDEPS),$($(x))))