pixman: disable vmx for powerpc CS toolchains

The ppc CS toolchains have flaky VMX (AKA altivec) implementation
causing build failure. Disable it for these toolchains. Fixes:
http://autobuild.buildroot.net/results/3b4/3b4cda40f074578f6b35b1fb381ba37b93174e86/

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Tested-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/pixman/pixman.mk

@@ -32,5 +32,10 @@ ifeq ($(BR2_TOOLCHAIN_EXTERNAL_CODESOURCERY_NIOSII201405),y)
 PIXMAN_CONF_ENV += CFLAGS="$(TARGET_CFLAGS) -DPIXMAN_NO_TLS"
 endif
 
+# Altivec detection isn't reliable for CS toolchains
+ifeq ($(BR2_TOOLCHAIN_EXTERNAL_CODESOURCERY_POWERPC201103)$(BR2_TOOLCHAIN_EXTERNAL_CODESOURCERY_POWERPC201009),y)
+PIXMAN_CONF_OPTS += --disable-vmx
+endif
+
 $(eval $(autotools-package))
 $(eval $(host-autotools-package))