gcc: pass MAKEINFO=missing in the environment rather than as a ./configure arg

Fixes a build issue with the avr32 toolchain:

http://jenkins.free-electrons.com/job/buildroot/config=atngw100_defconfig/104/

Invalid configuration `MAKEINFO=missing': machine `MAKEINFO=missing' not
recognized

Instead pass it in the environment of ./configure, similar to how it was
done originally in 62322acb2ce (toolchain/gcc: disable makeinfo).

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

package/gcc/gcc-final/gcc-final.mk

@@ -55,6 +55,9 @@ endif
 HOST_GCC_FINAL_CONF_OPT += \
 	$(call qstrip,$(BR2_EXTRA_GCC_CONFIG_OPTIONS))
 
+HOST_GCC_FINAL_CONF_ENV = \
+	$(HOST_GCC_COMMON_CONF_ENV)
+
 # Make sure we have 'cc'
 define HOST_GCC_FINAL_CREATE_CC_SYMLINKS
 	if [ ! -e $(HOST_DIR)/usr/bin/$(GNU_TARGET_NAME)-cc ]; then \

package/gcc/gcc-initial/gcc-initial.mk

@@ -34,6 +34,9 @@ HOST_GCC_INITIAL_CONF_OPT = \
 	--disable-nls \
 	$(call qstrip,$(BR2_EXTRA_GCC_CONFIG_OPTIONS))
 
+HOST_GCC_INITIAL_CONF_ENV = \
+	$(HOST_GCC_COMMON_CONF_ENV)
+
 HOST_GCC_INITIAL_MAKE_OPT = all-gcc
 HOST_GCC_INITIAL_INSTALL_OPT = install-gcc
 

package/gcc/gcc-intermediate/gcc-intermediate.mk

@@ -33,6 +33,9 @@ HOST_GCC_INTERMEDIATE_CONF_OPT = \
 	--disable-nls \
 	$(call qstrip,$(BR2_EXTRA_GCC_CONFIG_OPTIONS))
 
+HOST_GCC_INTERMEDIATE_CONF_ENV = \
+	$(HOST_GCC_COMMON_CONF_ENV)
+
 HOST_GCC_INTERMEDIATE_MAKE_OPT = all-gcc
 ifeq ($(BR2_GCC_SUPPORTS_FINEGRAINEDMTUNE),y)
 HOST_GCC_INTERMEDIATE_MAKE_OPT += all-target-libgcc

package/gcc/gcc.mk

@@ -96,7 +96,11 @@ HOST_GCC_COMMON_CONF_OPT = \
 	--disable-libssp \
 	--disable-multilib \
 	--with-gmp=$(HOST_DIR)/usr \
-	--with-mpfr=$(HOST_DIR)/usr \
+	--with-mpfr=$(HOST_DIR)/usr
+
+# Don't build documentation. It takes up extra space / build time,
+# and sometimes needs specific makeinfo versions to work
+HOST_GCC_COMMON_CONF_ENV = \
 	MAKEINFO=missing
 
 # http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43810