assimp: fix gcc version condition

In commit 68cebedeb977396f64f5f591f5e93f34fab8e0a8 ("assimp: work around
gcc bug on SuperH"), a work around was added to make the package build
with gcc on SuperH. The condition included a test on the gcc version,
which was mistakenly done on the host gcc version, while a test on the
target gcc version was intended.

Thanks to Peter Korsgaard for spotting the issue.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/assimp/assimp.mk

@@ -20,7 +20,7 @@ endif
 # not passed) in gcc versions 5.x or older. The -Os optimization level
 # causes a "unable to find a register to spill in class
 # ‘GENERAL_REGS’" error. -O2 works fine.
-ifeq ($(BR2_sh):$(BR2_STATIC_LIBS):$(BR2_HOST_GCC_AT_LEAST_6),y:y:)
+ifeq ($(BR2_sh):$(BR2_STATIC_LIBS):$(BR2_TOOLCHAIN_GCC_AT_LEAST_6),y:y:)
 ASSIMP_CXXFLAGS += -O2
 endif