package/gtkiostream: add BR2_PACKAGE_GTKIOSTREAM_ARCH_SUPPORTS

gtkiostream only supports little-endian since its addition in commit
fab48302865e5c0c98d91b696bc90e75e38189bb resulting in the following
build failure:

In file included from BitStream.C:23:
../include/BitStream.H:35:2: error: #error "iobitstream not tested on big endian systems"
   35 | #error "iobitstream not tested on big endian systems"
      |  ^~~~~

Fixes: fab48302865e5c0c98d91b696bc90e75e38189bb
 - http://autobuild.buildroot.org/results/aec24d92cc2196596413cf509d686f1f8d1eca95

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

package/gtkiostream/Config.in

@@ -1,5 +1,10 @@
+config BR2_PACKAGE_GTKIOSTREAM_ARCH_SUPPORTS
+	bool
+	default y if BR2_ENDIAN = "LITTLE"
+
 config BR2_PACKAGE_GTKIOSTREAM
 	bool "gtkiostream"
+	depends on BR2_PACKAGE_GTKIOSTREAM_ARCH_SUPPORTS
 	depends on BR2_INSTALL_LIBSTDCPP # eigen
 	depends on BR2_TOOLCHAIN_HAS_THREADS
 	select BR2_PACKAGE_ALSA_LIB_MIXER if BR2_PACKAGE_ALSA_LIB
@@ -14,5 +19,6 @@ config BR2_PACKAGE_GTKIOSTREAM
 	  https://github.com/flatmax/gtkiostream
 
 comment "gtkiostream needs a toolchain w/ C++, threads"
+	depends on BR2_PACKAGE_GTKIOSTREAM_ARCH_SUPPORTS
 	depends on !BR2_INSTALL_LIBSTDCPP || \
 		!BR2_TOOLCHAIN_HAS_THREADS