[gimp] configure: Fix the usage of sed on FreeBSD

[Jehan Pagès <jehanp src gnome org>]

commit bccaf39dc9a61d9592b7650bcf1b243e7f6ae314
Author: Ting-Wei Lan <lantw src gnome org>
Date:   Thu Dec 28 01:45:02 2017 +0800

    configure: Fix the usage of sed on FreeBSD
    
    FreeBSD requires the right brace to be preceded by a newline. Putting it
    on the same line as other commands is not allowed.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=791989

 configure.ac |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 10ba3b6..0350cc6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2713,7 +2713,8 @@ m4_define([generate_po_makefile], [
         "$srcdir/$1/POTFILES.in" | sed '$!s/$/ \\/' >"$1/POTFILES" && \
     sed -e "/^# This comment gets stripped out/ {"  \
         -e 'r $1/POTFILES'                          \
-        -e "d }" "$1/Makefile.in" >"$1/Makefile" && \
+        -e "d" -e "}"                               \
+        "$1/Makefile.in" >"$1/Makefile" && \
     touch "$1/stamp-it"
     ])
 ])