Make gen-XX-const scripts work with llvm-as
The gen-as-const and gen-py-const scripts are used to generate integer constant definitions from a list of constant C-expressions. This is achieved by generating a C program with inline `asm` statements, that depend on these constant expressions. During compilation, the constant expressions are evaluated, and included in the inline asm. The build process generates only the assembly, and then used `sed` to extract the values from the assembly text. This is clever. It allows the build process to extract the value of C statements built under the target architecture. The implementation is a bit fragile, but it is not immediately obvious to me how it could be improved. This change slightly modifies `gen-as-const` and `gen-py-const` to emit valid assembly directives instead of invalid directives that were previously emitted. Since the values are extracted via string parsing, this has no effect on the values extracted. This is needed because the LLVM assembler validates all statements before emitting them, whereas it appears GCC will literally emit any `asm` directives without validation or recognition.
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