build: fix CMake assembly builds with ccache

CMAKE_ASM_COMPILER is automatically set to CMAKE_C_COMPILER by CMake, but
CMAKE_C_COMPILER_ARG1 is lost. This causes assembly builds to fail when ccache
is enabled (for example the package fastd on x86).

Fix this by explicitly defining CMAKE_ASM_COMPILER and CMAKE_ASM_COMPILER_ARG1.

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>

SVN-Revision: 45119