[mini-patch] Fix a set of warnings

[Tim Van Holder]

This small patch allows automake to run for the CVS tree
of gas without producing these warnings:

Use of uninitialized value in substitution (s///) at automake line 1587.
Use of uninitialized value in concatenation (.) at automake line 188.
Use of uninitialized value in quotemeta at automake line 6972.

Index: automake.in
===================================================================
RCS file: /cvs/automake/automake/automake.in,v
retrieving revision 1.1139
diff -u -u -r1.1139 automake.in
--- automake.in 2001/06/15 01:25:11     1.1139
+++ automake.in 2001/06/16 19:11:47
@@ -1584,7 +1584,7 @@
            my $flags = $lang->flags || '';
            my $val = "${derived}_${flags}";
 
-           (my $obj_compile = $lang->compile) =~ s/\(AM_$flags/\($val/;
+           (my $obj_compile = $lang->compile || '') =~ s/\(AM_$flags/\($val/;
            my $obj_ltcompile = '$(LIBTOOL) --mode=compile ' . $obj_compile;
 
            # We _need_ `-o' for per object rules.