libgomp: Hopefully avoid false positive warnings in env.c on solaris

libgomp: Hopefully avoid false positive warnings in env.c on solaris

> the patch also breaks bootstrap on both i386-pc-solaris2.11 and
> sparc-sun-solaris2.11:
>
> /vol/gcc/src/hg/master/local/libgomp/env.c: In function 'initialize_env':
> /vol/gcc/src/hg/master/local/libgomp/env.c:414:16: error: 'new_offload' may be used uninitialized in this function [-Werror=maybe-uninitialized]
>   414 |       *offload = new_offload;
>       |       ~~~~~~~~~^~~~~~~~~~~~~
> /vol/gcc/src/hg/master/local/libgomp/env.c:384:30: note: 'new_offload' was declared here
>   384 |   enum gomp_target_offload_t new_offload;
>       |                              ^~~~~~~~~~~

I can't reproduce that, but I fail to see why we need two separate
variables, one with actual value and one tracking if the value is valid.

So, I'm going with:

2020-10-21  Jakub Jelinek  <jakub@redhat.com>

	* env.c (parse_target_offload): Change new_offload var type to int,
	preinitialize to -1, remove found var and test new_offload != -1
	instead of found.