Configurations/10-main.conf: add -fno-common back to darwin-ppc-cc.

-fno-common was removed for all Darwin targets in
0c873419 with rationale "it's either
'ranlib -c' or '-fno-common'." However, it's still absolutely required
in 32-bit darwin-ppc-cc. And when trying things out I didn't quite
see why it was formulated as one-or-another choice, as 'ranlib -c'
shouldn't [and doesn't] have problems with object modules without
commons. [Well, to be frank, I didn't manage to reproduce the problem
the modification was meaning to resolve either...]
Reviewed-by: NRich Salz <rsalz@openssl.org>

Configurations/10-main.conf

@@ -1647,6 +1647,7 @@ my %targets = (
         inherit_from     => [ "darwin-common", asm("ppc32_asm") ],
         cflags           => add("-arch ppc -std=gnu9x -Wa,-force_cpusubtype_ALL"),
         cppflags         => add("-DB_ENDIAN"),
+        shared_cflag     => add("-fno-common"),
         perlasm_scheme   => "osx32",
     },
     "darwin64-ppc-cc" => {