[gnome-latex] build: use GLIB_REQUIRED_VERSION variable for --target-glib vala flag

[Sébastien Wilmet <swilmet src gnome org>]

commit 58a8d3fbc2e930f530868a5a46132c64675b627a
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sun Apr 8 13:29:58 2018 +0200

    build: use GLIB_REQUIRED_VERSION variable for --target-glib vala flag
    
    Since I often forget to update the --target-glib when I change
    GLIB_REQUIRED_VERSION. The comment was not sufficiently visible.

 configure.ac    | 1 -
 src/Makefile.am | 2 +-
 2 files changed, 1 insertion(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 206c5da..d1b8a14 100644
--- a/configure.ac
+++ b/configure.ac
@@ -28,7 +28,6 @@ LT_PREREQ([2.2])
 LT_INIT
 
 # Required dependencies versions
-# Update also the --target-glib option in src/Makefile.am.
 GLIB_REQUIRED_VERSION="2.56"
 GTK_REQUIRED_VERSION="3.22"
 GTKSOURCEVIEW_REQUIRED_VERSION="4.0"
diff --git a/src/Makefile.am b/src/Makefile.am
index 2a134fa..8aa0c5c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -12,7 +12,7 @@ AM_VALAFLAGS =                                        \
        --pkg gspell-1                          \
        --pkg gee-0.8                           \
        --pkg posix                             \
-       --target-glib=2.50                      \
+       --target-glib=@GLIB_REQUIRED_VERSION@   \
        --vapidir liblatexila                   \
        --vapidir $(abs_builddir)/liblatexila   \
        --pkg latexila