When building with clang, we get:
error: unknown warning option '-Wmissing-parameter-type' [-Werror,-Wunknown-warning-option]
This is because clang only warns by default when encountering an unknown
warning option, and the probe for supported warning flags is done
without -Werror. All flags are therefore accepted by configure, but
then it breaks when actually compiling a source file with -Werror.
This is equivalent to this commit in gdb:
3e019bdc20eb81b91ab5bc774386201b874c0bac
gdb: Use -Werror when checking for (un)supported warning flags
We then see some other compilation errors when building with clang and
-Werror, they can be dealt with later.
1f195bc327