kbuild: LLVMLinux: Fix LINUX_COMPILER definition script for compilation with clang

When building the LINUX_COMPILER definition, instead of merely taking the last
line from "$(CC) -v", grep for ' version ' in the output. This supports both
gcc and clang.

Signed-off-by: Jan-Simon Möller <dl9pf@gmx.de>
Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Cc: PaX Team <pageexec@freemail.hu>
LLVMLinux: Remove warning about returning an uninitialized variable

Fix uninitialized return code in default case in cmpxchg-local.h

This patch fixes the code to prevent an uninitialized return value that is detected
when compiling with clang. The bug produces numerous warnings when compiling the
Linux kernel with clang.

Signed-off-by: Behan Webster <behanw@converseincode.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Acked-by: David Howells <dhowells@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
LLVMLinux: Add support for clang to compiler.h and new compiler-clang.h

Add a compiler-clang.h file to add specific macros needed for compiling the
kernel with clang.

Initially the only override required is the macro for silencing the
compiler for a purposefully uninintialized variable.

Author: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Behan Webster <behanw@converseincode.com>
arm: LLVMLinux: Add current_stack_pointer macro for ARM

The current kernel code uses a named register to get the stack pointer which is
only supported in gcc. For clang an alternative is to use a macro to get the
current stack pointer using ASM (which is less efficient than a named
resgiter). Long term the LLVMLinux project is hoping to introduce a new
__builtin_stack_pointer() which will be added to both LLVM and gcc.

Author: Behan Webster <behanw@converseincode.com>
Signed-off-by: Behan Webster <behanw@converseincode.com>
Reviewed-by: Jan-Simon Möller <dl9pf@gmx.de>
Reviewed-by: Mark Charlebois <charlebm@gmail.com>
Documentation: LLVMLinux: Update Documentation/dontdiff

Clang has a few other kinds of derived files which shouldn't be added to a
patch. Add them to the Documentation/dontdiff file to prevent this.

Signed-off-by: Jan-Simon Möller <dl9pf@gmx.de>
Signed-off-by: Behan Webster <behanw@converseincode.com>
Cc: PaX Team <pageexec@freemail.hu>
arm: LLVMLinux: Provide __aeabi_* symbols which are needed for clang

These symbols are required when compiling the Linux kernel for arch ARM with
clang.

Author: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Mark Charlebois <charlebm@gmail.com>
Signed-off-by: Behan Webster <behanw@converseincode.com>

Conflicts:
	arch/arm/lib/Makefile