[LyX/2.4.x] Add explicit check for EGREP in configure.ac

[Jean-Marc Lasgouttes]

commit 2882bed1abcce146107b936f81d77ecd0f051bc0
Author: Jean-Marc Lasgouttes <lasgouttes at lyx.org>
Date:   Fri Jul 12 16:02:53 2024 +0200

    Add explicit check for EGREP in configure.ac
    
    It is used in lib/Makefile.am and we were relying some autoconf macros
    to define it as a side-effect. This is not the case anymore as of
    autoconf 2.72.
    
    (cherry picked from commit 31cde7247638a50c2302744984732064505b7d85)
---
 configure.ac | 3 +++
 status.24x   | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index d05e633a78..fc6a3f6319 100644
--- a/configure.ac
+++ b/configure.ac
@@ -124,6 +124,9 @@ AC_SUBST([HAVE_WCHAR_T])
 # Needed for Mingw-w64
 AC_TYPE_LONG_LONG_INT
 
+# egrep is used in lib/Makefile.am
+AC_PROG_EGREP
+
 ### We need iconv for unicode support (Qt frontend requires it too)
 LYX_USE_INCLUDED_ICONV
 
diff --git a/status.24x b/status.24x
index 538c881b43..6414a40abb 100644
--- a/status.24x
+++ b/status.24x
@@ -86,4 +86,4 @@ What's new
 
 * BUILD/INSTALLATION
 
-
+- Fix 'make install' target for autotools builds with autoconf >= 2.72.