build: avoid bootstrap failure when $GZIP is set

Running "GZIP=-9 ./bootstrap" would fail right away, because the
tool-version-checking code would treat the upper-cased program name
as an environment variable name and if that has a value use the
result as the application name.  That works fine for automake,
autoconf, etc. but not for gzip.
* bootstrap (check_versions): Do not treat $GZIP as a program name.
If defined at all, it is supposed to list gzip options.
Reported by Alan Curry in http://debbugs.gnu.org/8609

diff --git a/bootstrap b/bootstrap
index f004ad3..c45ae48 100755 (executable)
--- a/bootstrap
+++ b/bootstrap
@@ -1,6 +1,6 @@
 #! /bin/sh
 # Print a version string.
-scriptversion=2011-03-03.12; # UTC
+scriptversion=2011-05-03.08; # UTC
 
 # Bootstrap this package from checked-out sources.
 
@@ -405,7 +405,10 @@ check_versions() {
     # Honor $APP variables ($TAR, $AUTOCONF, etc.)
     appvar=`echo $app | tr '[a-z]-' '[A-Z]_'`
     test "$appvar" = TAR && appvar=AMTAR
-    eval "app=\${$appvar-$app}"
+    case $appvar in
+        GZIP) ;; # Do not use $GZIP:  it contains gzip options.
+        *) eval "app=\${$appvar-$app}" ;;
+    esac
     inst_ver=$(get_version $app)
     if [ ! "$inst_ver" ]; then
       echo "$me: Error: '$app' not found" >&2