re-add archscripts removal patch for linux 4.19.90

forward-ported from the now-removed 4.4.10 patch, needed to fix #8,
spurious dependency on host elf.h header. I checked x86 and mips which
seem to be the only archs with archscripts rules, and these rules have
nothing to do with building headers, so omitting them should still be
safe.

patches/linux-4.19.90/0101-archscripts.diff

@@ -0,0 +1,11 @@
+--- linux-4.19.90.orig/Makefile	2019-12-17 14:36:04.000000000 -0500
++++ linux-4.19.90/Makefile	2020-01-30 22:06:04.216550425 -0500
+@@ -1173,7 +1173,7 @@
+ archscripts:
+ 
+ PHONY += __headers
+-__headers: $(version_h) scripts_basic uapi-asm-generic archheaders archscripts
++__headers: $(version_h) scripts_basic uapi-asm-generic archheaders
+ 	$(Q)$(MAKE) $(build)=scripts build_unifdef
+ 
+ PHONY += headers_install_all