[PATCH v2] ARM: error out if compiling ARMv6 using Clang before 8.0

The kernel passes the ArmV6K architecture to the compiler when
using the multi platform selection and enabling ARMv6. Clang
older than version 8.0 emit assembly with an non-existing CPU,
which then makes the GNU assembler fail. Warn users when
compiling ARMv6 using Clang before 8.0.

Suggested-by: Russell King <linux@armlinux.org.uk>
Signed-off-by: Stefan Agner <stefan@agner.ch>
Link: https://github.com/ClangBuiltLinux/linux/issues/55
---
 include/linux/compiler-clang.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index b1ce500fe8b3..9df8713bef38 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h

@@ -3,6 +3,10 @@
 #error "Please don't include <linux/compiler-clang.h> directly, include <linux/compiler.h> instead."
 #endif
 
+#if defined(CONFIG_ARCH_MULTI_V6) && CONFIG_CLANG_VERSION < 80000
+#error "Sorry, your compiler is too old - please upgrade it."
+#endif
+
 /* Some compiler specific definitions are overwritten here
  * for Clang compiler
  */

-- 
2.19.1