fix leon3 toolchain building

embedded-test.sh

@@ -937,7 +937,7 @@ get_arch_info() {
       allowed_libc="uclibc-ng"
       runtime_test=""
       allowed_tests="toolchain"
-      default_uclibc_ng="ADK_APPLIANCE=toolchain ADK_TARGET_ARCH=sparc ADK_TARGET_CPU=leon3 ADK_TARGET_SYSTEM=generic-sparc"
+      default_uclibc_ng="ADK_APPLIANCE=toolchain ADK_TARGET_OS=linux ADK_TARGET_ARCH=sparc ADK_TARGET_CPU=leon3 ADK_TARGET_SYSTEM=generic-sparc"
       cpu_arch=leon
       suffix=${cpu_arch}
       ;;