Config.in: add symbols for BR2_HOST_GCC_AT_LEAST_X_Y

Some host packages need a recent gcc version. Add symbols to Config.in
to specify the HOSTCC version. The values are passed through the
environment, and this environment is generated in a new support script.

Also update the documentation to mention the new symbols.

[Thomas: simplify by using only make logic instead of an external
shell script.]

Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

Config.in

@@ -18,6 +18,30 @@ config BR2_EXTERNAL
 	string
 	option env="BR2_EXTERNAL"
 
+# Hidden config symbols for packages to check system gcc version
+config BR2_HOST_GCC_VERSION
+	string
+	option env="HOST_GCC_VERSION"
+
+config BR2_HOST_GCC_AT_LEAST_4_7
+	bool
+	default y if BR2_HOST_GCC_VERSION = "4 7"
+
+config BR2_HOST_GCC_AT_LEAST_4_8
+	bool
+	default y if BR2_HOST_GCC_VERSION = "4 8"
+	select BR2_HOST_GCC_AT_LEAST_4_7
+
+config BR2_HOST_GCC_AT_LEAST_4_9
+	bool
+	default y if BR2_HOST_GCC_VERSION = "4 9"
+	select BR2_HOST_GCC_AT_LEAST_4_8
+
+config BR2_HOST_GCC_AT_LEAST_5
+	bool
+	default y if BR2_HOST_GCC_VERSION = "5"
+	select BR2_HOST_GCC_AT_LEAST_4_9
+
 # Hidden boolean selected by packages in need of Java in order to build
 # (example: xbmc)
 config BR2_NEEDS_HOST_JAVA

Makefile

@@ -293,6 +293,14 @@ HOSTRANLIB := $(shell which $(HOSTRANLIB) || type -p $(HOSTRANLIB) || echo ranli
 export HOSTAR HOSTAS HOSTCC HOSTCXX HOSTLD
 export HOSTCC_NOCCACHE HOSTCXX_NOCCACHE
 
+HOSTCC_VERSION := $(shell $(HOSTCC_NOCCACHE) --version | \
+	sed -n -r 's/^.* ([0-9]*)\.([0-9]*)\.([0-9]*)[ ]*.*/\1 \2/p')
+
+# For gcc >= 5.x, we only need the major version.
+ifneq ($(firstword $(HOSTCC_VERSION)),4)
+HOSTCC_VERSION := $(firstword $(HOSTCC_VERSION))
+endif
+
 # Make sure pkg-config doesn't look outside the buildroot tree
 HOST_PKG_CONFIG_PATH := $(PKG_CONFIG_PATH)
 unexport PKG_CONFIG_PATH
@@ -724,6 +732,7 @@ COMMON_CONFIG_ENV = \
 	KCONFIG_TRISTATE=$(BUILD_DIR)/buildroot-config/tristate.config \
 	BR2_CONFIG=$(BR2_CONFIG) \
 	BR2_EXTERNAL=$(BR2_EXTERNAL) \
+	HOST_GCC_VERSION="$(HOSTCC_VERSION)" \
 	SKIP_LEGACY=
 
 xconfig: $(BUILD_DIR)/buildroot-config/qconf outputmakefile

docs/manual/adding-packages-directory.txt

@@ -283,6 +283,13 @@ use in the comment.
 ** Comment string: +gcc >= X.Y+ and/or `gcc <= X.Y` (replace
    +X.Y+ with the proper version)
 
+* Host GCC version
+** Dependency symbol: +BR2_HOST_GCC_AT_LEAST_X_Y+, (replace
+   +X_Y+ with the proper version, see +Config.in+)
+** Comment string: no comment to be added
+** Note that it is usually not the package itself that has a minimum
+   host GCC version, but rather a host-package on which it depends.
+
 * C library
 ** Dependency symbol: +BR2_TOOLCHAIN_USES_GLIBC+,
    +BR2_TOOLCHAIN_USES_MUSL+, +BR2_TOOLCHAIN_USES_UCLIBC+