Address compiler diagnostics in libgomp.oacc-c-c++-common/pr87835.c

Address compiler diagnostics in libgomp.oacc-c-c++-common/pr87835.c

    source-gcc/libgomp/testsuite/libgomp.oacc-c-c++-common/pr87835.c: In function 'main':
    source-gcc/libgomp/testsuite/libgomp.oacc-c-c++-common/pr87835.c:45: warning: ignoring #pragma loop gang [-Wunknown-pragmas]
       45 |     #pragma loop gang
          |
    source-gcc/libgomp/testsuite/libgomp.oacc-c-c++-common/pr87835.c:19:7: warning: unused variable 'b' [-Wunused-variable]
       19 |   int b[n];
          |       ^

	libgomp/
	PR target/87835
	* testsuite/libgomp.oacc-c-c++-common/pr87835.c: Update.

From-SVN: r271004