[PATCH groff] Allow manually disabling building the Texinfo manual

[onf]

add option --disable-info-doc to ./configure which disables building
the Texinfo manual as if makeinfo was missing except that no warnings
are emitted
---
As discussed in https://savannah.gnu.org/bugs/index.php?66583#comment15

 configure.ac |  6 +++++-
 doc/doc.am   |  2 +-
 m4/groff.m4  | 10 +++++++++-
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/configure.ac b/configure.ac
index e9420c9ca..af69482d0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -41,6 +41,9 @@ AM_INIT_AUTOMAKE([subdir-objects])
 
 AM_SILENT_RULES([yes])
 
+# disable building of texinfo manual if desired
+GROFF_USE_INFO_DOC
+
 # checks for programs
 AC_PROG_CC
 AC_PROG_CXX
@@ -195,7 +198,8 @@ AM_CONDITIONAL([USE_GROFF_ALLOCATOR],
 AM_CONDITIONAL([HAVE_GHOSTSCRIPT], [test "$GHOSTSCRIPT" != no \
                 && test "$GHOSTSCRIPT" != missing])
 AM_CONDITIONAL([HAVE_URW_FONTS], [test "$groff_have_urw_fonts" = yes ])
-AM_CONDITIONAL([HAVE_MAKEINFO], [test "$groff_have_makeinfo" = yes ])
+AM_CONDITIONAL([WANT_MAKEINFO], [test "$groff_have_makeinfo" = yes \
+               && test "$groff_want_makeinfo" != no])
 AM_CONDITIONAL([HAVE_TEXI2DVI], [test "$groff_have_texi2dvi" = yes ])
 AM_CONDITIONAL([USE_TEX], [test "$groff_use_tex" = yes ])
 
diff --git a/doc/doc.am b/doc/doc.am
index a4f0df6cf..6d6eacdc8 100644
--- a/doc/doc.am
+++ b/doc/doc.am
@@ -542,7 +542,7 @@ endif
 #info_TEXINFOS = doc/groff.texi
 #doc_groff_TEXINFOS = doc/fdl.texi
 
-if HAVE_MAKEINFO
+if WANT_MAKEINFO
 GROFF_INFO = doc/groff.info
 GROFF_TXT = doc/groff.txt
 GROFF_HTML = doc/groff.html
diff --git a/m4/groff.m4 b/m4/groff.m4
index 0fb6a7765..e7b1abcbf 100644
--- a/m4/groff.m4
+++ b/m4/groff.m4
@@ -284,7 +284,7 @@ AC_DEFUN([GROFF_GROPDF_DEPENDENCIES_CHECK], [
 AC_DEFUN([GROFF_MAKEINFO_PROGRAM_NOTICE], [
   AC_REQUIRE([GROFF_PROG_MAKEINFO])
 
-  if test "$groff_have_makeinfo" = no
+  if test "$groff_have_makeinfo" = no && test "$groff_want_info" != no
   then
     AC_MSG_NOTICE([groff's Texinfo manual will not be generated.
 
@@ -1866,3 +1866,11 @@ allocator for C++ new/delete])],
     [test "$enableval" = yes && groff_use_own_allocator=yes],
     [groff_use_own_allocator=no])
 ])
+
+AC_DEFUN([GROFF_USE_INFO_DOC], [
+  AC_ARG_ENABLE([info-doc],
+    [AS_HELP_STRING([--disable-info-doc], [disable building \
+the texinfo manual])],
+    [test "$enableval" = no && groff_want_info=no],
+    [groff_want_info=yes])
+])
-- 
2.47.0