[COMMITTED] Fix global_vars_f90_init test failure

[Wilco Dijkstra]

Add a missing extern to ensure the test passes with -fno-common.
Committed as obvious.

ChangeLog:
2019-11-21  Wilco Dijkstra  <wdijk...@arm.com>

    testsuite/
        * gfortran.dg/global_vars_f90_init_driver.c: Add missing extern.
--
diff --git a/gcc/testsuite/gfortran.dg/global_vars_f90_init_driver.c 
b/gcc/testsuite/gfortran.dg/global_vars_f90_init_driver.c
index 
7869c83f71254d3269404331aac56c38abbc7521..27ba7e656d0c354ed8dc504c0cd42855e309cdaa
 100644
--- a/gcc/testsuite/gfortran.dg/global_vars_f90_init_driver.c
+++ b/gcc/testsuite/gfortran.dg/global_vars_f90_init_driver.c
@@ -1,5 +1,5 @@
 /* initialized by fortran */
-int i;
+extern int i;
 void test_globals(void);
 
 extern void abort(void);