Assembly files (.s) cause "execvp" error with incorrect tool path

[dhairs]

When using a startup.s file that defines reset handlers, etc. (like from stm32), the toolchain doesn't accept the assembly file in cc_binary srcs and causes an error when looking for the assembler.

[danielfu11]

I think this is because:

Pure assembler files (.s, .asm) are not preprocessed and are typically built using the assembler. Preprocessed assembly files (.S) are preprocessed and are typically built using the C/C++ compiler.

(source)

And as_files is not defined and so bazel is not able to find the assembler? @hexdae can you please confirm if this is the issue?

[danielfu11]

I reproduced the issue in the raspberry_pi example and the as_files fix seems to work? #84

[hexdae]

Ah yes Smart. This should work