build: Drop --enable-rebuilds configure option

It is outdated and no longer effectively used. It was originally in
place to prevent rebuilding generated files (from a tarball) if the
right build tools (awk, Perl, indent) were not available. However, we no
longer use indent, we have hard-required awk for a while, and the only
places the @REBUILD@ substitution was still used were for
glib-genmarshal, which has recently been rewritten in Python (so no
longer depends on whether Perl is available).

Drop the whole lot.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

https://bugzilla.gnome.org/show_bug.cgi?id=694723

configure.ac

@@ -252,10 +252,6 @@ AC_ARG_ENABLE(mem_pools,
               [AS_HELP_STRING([--disable-mem-pools],
 			      [disable all glib memory pools])],,
 	      [disable_mem_pools=no])
-AC_ARG_ENABLE(rebuilds,
-              [AS_HELP_STRING([--disable-rebuilds],
-                              [disable all source autogeneration rules])],,
-              [enable_rebuilds=yes])
 
 GLIB_TESTS
 
@@ -354,20 +350,8 @@ AC_SUBST(GLIB_EXTRA_CFLAGS)
 
 AC_EXEEXT
 
-# define a MAINT-like variable REBUILD which is set if Perl
-# and awk are found, so autogenerated sources can be rebuilt
 AC_PROG_AWK
 AC_CHECK_PROGS(PERL, [perl5 perl])
-# We would like indent, but don't require it.
-AC_CHECK_PROG(INDENT, indent, indent)
-REBUILD=\#
-if test "x$enable_rebuilds" = "xyes" && \
-     test -n "$PERL" && \
-     $PERL -e 'exit !($] >= 5.002)' > /dev/null 2>&1 && \
-     test -n "$AWK" ; then
-  REBUILD=
-fi
-AC_SUBST(REBUILD)
 
 # option to specify python interpreter to use; this just sets $PYTHON, so that
 # we will fallback to reading $PYTHON if --with-python is not given, and