[gparted] Resolve messages from configure in VPATH build (!103)

[Curtis Gedak <gedakc src gnome org>]

commit 053691378c6cc3d153dc32b4d75da50f901e0062
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Tue May 31 12:21:04 2022 +0100

    Resolve messages from configure in VPATH build (!103)
    
    Even though this is fixed the execution of configure as part of make
    distcheck outputs this:
        checking whether po/Makefile.in.in deletes intltool cache lock file... /usr/bin/grep: 
po/Makefile.in.in: No such file or directory
        /usr/bin/sed: can't read po/Makefile.in.in: No such file or directory
        /usr/bin/grep: po/Makefile.in.in: No such file or directory
        no
    
    make distcheck [1] performs a VPATH build with a read-only srcdir and
    a separate writable build directory with files split between the two.
    The relevant layout looks like:
        ./gparted-1.4.0-git/configure
        ./gparted-1.4.0-git/po/Makefile.in.in
        ./gparted-1.4.0-git/_build/sub/
    
    And make distcheck runs configure like this:
        cd ./gparted-1.4.0-git/_build/sub
        ../../configure --srcdir=../..
    
    The file is ../../po/Makefile.in.in in this case, so not found by the
    existing check.  A simple investigation technique is to run make
    distcheck, kill it shortly after configure completes and examine the
    build tree.  Definitely before make distcheck completes successfully and
    deletes everything.
    
    Fix by using $srcdir prefix to access the file.  Also handle the case of
    po/Makefile.in.in not existing, although this doesn't now occur in the
    scenario fixed by this commit.  And only patch the file if it's
    writable, another case that doesn't occur in this scenario.
    
    Relevant output line from configure run by make distcheck now looks
    like:
        checking whether po/Makefile.in.in deletes intltool cache lock file... yes
    
    [1] GNU Automake, 14.4 Checking the Distribution
        https://www.gnu.org/software/automake/manual/html_node/Checking-the-Distribution.html
    
    Closes !103 - Fix make distcheck failure found in GitLab CI job
                  unbuntu_test

 configure.ac | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index d9320c89..0e9ec191 100644
--- a/configure.ac
+++ b/configure.ac
@@ -64,11 +64,14 @@ dnl needed with intltool >= 0.51.0-5.1, but just always fix as that is
 dnl simpler and safe.
 AC_MSG_CHECKING([whether po/Makefile.in.in deletes intltool cache lock file])
 file='po/Makefile.in.in'
-if $FGREP -q '.intltool-merge-cache.lock' "$file"; then
+if test ! -f "$srcdir/$file"; then
+       AC_MSG_RESULT([not applicable])
+elif $FGREP -q '.intltool-merge-cache.lock' "$srcdir/$file" 2> /dev/null; then
        AC_MSG_RESULT([yes])
 else
-       $SED -i '/rm -f .intltool-merge-cache/s/$/ .intltool-merge-cache.lock/' "$file"
-       if $FGREP -q '.intltool-merge-cache.lock' "$file"; then
+       test -w "$srcdir/$file" && \
+       $SED -i '/rm -f .intltool-merge-cache/s/$/ .intltool-merge-cache.lock/' "$srcdir/$file" 2> /dev/null
+       if $FGREP -q '.intltool-merge-cache.lock' "$srcdir/$file" 2> /dev/null; then
                AC_MSG_RESULT([fixed])
        else
                AC_MSG_RESULT([no])