Empirically these need to come from most specfic to least specific.
The error message is as follows:
In file included from test/c/main.c:1:
In file included from external/zig_sdk/lib/libcxx/include/stdio.h:107:
In file included from external/zig_sdk/lib/libc/include/generic-glibc/stdio.h:38:
external/zig_sdk/lib/libc/include/generic-glibc/bits/types.h:139:3: error:
# error
^
external/zig_sdk/lib/libc/include/generic-glibc/bits/types.h:145:1: error: unknown type name '__STD_TYPE'
__STD_TYPE __DEV_T_TYPE __dev_t; /* Type of device numbers. */
Dissected `generic-glibc/bits/types.h:#error`:
#if __WORDSIZE == 32
<...>
# define __STD_TYPE __extension__ typedef
#elif __WORDSIZE == 64
<...>
# define __STD_TYPE typedef
#else
# error
#endif
So we do not have the `__WORDSIZE`. Where does that come from? Probably from a
directory that has an `x86_64` in it. How does that get included? Let's start
with `lib/libcxx/include/stdio.h`:
16 #include_next <stdio.h>
Now previously our `c++` command line looked like this:
external/zig_sdk/tools/c++ \
<...>
-Iexternal/zig_sdk/lib/include \
-Iexternal/zig_sdk/lib/libcxx/include \
-Iexternal/zig_sdk/lib/libcxxabi/include \
-Iexternal/zig_sdk/lib/libunwind/include \
-Iexternal/zig_sdk/lib/libc/include/generic-glibc \
-Iexternal/zig_sdk/lib/libc/include/any-linux-any \
-Iexternal/zig_sdk/lib/libc/include/x86_64-linux-gnu \
-Iexternal/zig_sdk/lib/libc/include/x86_64-linux-any \
-Iexternal/zig_sdk/lib/libc/include/x86-linux-any \
-Iexternal/zig_sdk/glibc-hacks \
<...>
So the next place it will find `stdio.h` is in `generic-glibc`, which already
uses the `__WORDSIZE`. If we make the "next" include to be the arch-specific
one instead of the generic-glibc, things start compiling again.
Fix the same fo musl.
