xen: Have Kconfig check $(CC)'s version

This import several files from Linux v5.3
 - scripts/Kconfig.include
 - scripts/clang-version.sh
 - scripts/gcc-version.sh
 and several config values from from Linux's init/Kconfig file.
But gcc-version.sh have been modified to return "0" when $CC isn't
GCC, like clang-version.sh do.

Files are copied into scripts/ directory because that's were the files
are found in Linux tree, and also because we are going to import more
of Kbuild from Linux which is located in scripts/.

CONFIG_GCC_VERSION and CONFIG_CC_IS_CLANG are going to be use in
follow-up patches.

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

xen/Kconfig

@@ -4,9 +4,25 @@
 #
 mainmenu "Xen/$(SRCARCH) $(XEN_FULLVERSION) Configuration"
 
+source "scripts/Kconfig.include"
+
 config BROKEN
 	bool
 
+config CC_IS_GCC
+	def_bool $(success,$(CC) --version | head -n 1 | grep -q gcc)
+
+config GCC_VERSION
+	int
+	default $(shell,$(BASEDIR)/scripts/gcc-version.sh $(CC))
+
+config CC_IS_CLANG
+	def_bool $(success,$(CC) --version | head -n 1 | grep -q clang)
+
+config CLANG_VERSION
+	int
+	default $(shell,$(BASEDIR)/scripts/clang-version.sh $(CC))
+
 source "arch/$(SRCARCH)/Kconfig"
 
 config DEFCONFIG_LIST

xen/Makefile

@@ -18,6 +18,8 @@ export XEN_CONFIG_EXPERT ?= n
 PYTHON_INTERPRETER	:= $(word 1,$(shell which python3 python python2 2>/dev/null) python)
 export PYTHON		?= $(PYTHON_INTERPRETER)
 
+export CC CXX LD
+
 export BASEDIR := $(CURDIR)
 export XEN_ROOT := $(BASEDIR)/..
 

xen/scripts/Kconfig.include

@@ -0,0 +1,39 @@
+# SPDX-License-Identifier: GPL-2.0-only
+# Kconfig helper macros
+
+# Convenient variables
+comma       := ,
+quote       := "
+squote      := '
+empty       :=
+space       := $(empty) $(empty)
+dollar      := $
+right_paren := )
+left_paren  := (
+
+# $(if-success,<command>,<then>,<else>)
+# Return <then> if <command> exits with 0, <else> otherwise.
+if-success = $(shell,{ $(1); } >/dev/null 2>&1 && echo "$(2)" || echo "$(3)")
+
+# $(success,<command>)
+# Return y if <command> exits with 0, n otherwise
+success = $(if-success,$(1),y,n)
+
+# $(failure,<command>)
+# Return n if <command> exits with 0, y otherwise
+failure = $(if-success,$(1),n,y)
+
+# $(cc-option,<flag>)
+# Return y if the compiler supports <flag>, n otherwise
+cc-option = $(success,$(CC) -Werror $(CLANG_FLAGS) $(1) -E -x c /dev/null -o /dev/null)
+
+# $(ld-option,<flag>)
+# Return y if the linker supports <flag>, n otherwise
+ld-option = $(success,$(LD) -v $(1))
+
+# check if $(CC) and $(LD) exist
+$(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
+$(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
+
+# gcc version including patch level
+gcc-version := $(shell,$(BASEDIR)/scripts/gcc-version.sh $(CC))

xen/scripts/clang-version.sh

@@ -0,0 +1,19 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# clang-version clang-command
+#
+# Print the compiler version of `clang-command' in a 5 or 6-digit form
+# such as `50001' for clang-5.0.1 etc.
+
+compiler="$*"
+
+if ! ( $compiler --version | grep -q clang) ; then
+	echo 0
+	exit 1
+fi
+
+MAJOR=$(echo __clang_major__ | $compiler -E -x c - | tail -n 1)
+MINOR=$(echo __clang_minor__ | $compiler -E -x c - | tail -n 1)
+PATCHLEVEL=$(echo __clang_patchlevel__ | $compiler -E -x c - | tail -n 1)
+printf "%d%02d%02d\\n" $MAJOR $MINOR $PATCHLEVEL

xen/scripts/gcc-version.sh

@@ -0,0 +1,25 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# gcc-version gcc-command
+#
+# Print the gcc version of `gcc-command' in a 5 or 6-digit form
+# such as `29503' for gcc-2.95.3, `30301' for gcc-3.3.1, etc.
+
+compiler="$*"
+
+if [ ${#compiler} -eq 0 ]; then
+	echo "Error: No compiler specified." >&2
+	printf "Usage:\n\t$0 <gcc-command>\n" >&2
+	exit 1
+fi
+
+if ! ( $compiler --version | head -n 1 | grep -q gcc ); then
+	echo 0
+	exit 1
+fi
+
+MAJOR=$(echo __GNUC__ | $compiler -E -x c - | tail -n 1)
+MINOR=$(echo __GNUC_MINOR__ | $compiler -E -x c - | tail -n 1)
+PATCHLEVEL=$(echo __GNUC_PATCHLEVEL__ | $compiler -E -x c - | tail -n 1)
+printf "%d%02d%02d\\n" $MAJOR $MINOR $PATCHLEVEL