Make improvements

- Fix unused local variable errors
- Remove yoinks from sigaction() header
- Add nox87 and aarch64 to github actions
- Fix cosmocc -fportcosmo in linking mode
- It's now possible to build `make m=llvm o/llvm/libc`

libc/vga/rlinit-vesa.S

@@ -435,7 +435,7 @@ _rlinit_vesa:
 	mov	$PC_VIDEO_TEXT,%al	# if text mode, simply say so
 	test	$0b00010000,%cl
 	jz	.ok4
-	cmp	$6,%es:0x1b(%di)	# if graphics mode, check if direct
+	cmpl	$6,%es:0x1b(%di)	# if graphics mode, check if direct
 	jnz	.fail4			# color; bail out if not
 	mov	%es:0x19(%di),%cl	# check actual color fields & bits
 	mov	%es:0x1f(%di),%ax	# per pixel, against a list

libc/vga/tty-klog.greg.c

@@ -39,7 +39,9 @@
  * @see libc/vga/tty-graph.inc
  */
 
+#ifndef __llvm__
 #pragma GCC optimize("s")
+#endif
 
 #define KLOGTTY
 #define MAYUNROLLLOOPS /* do not unroll loops; keep the code small! */