[newlib-cygwin] newlib: Enable automake silent rules

[Jon TURNEY <jturney@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=2b6f088ac3acba932b65322e40704bc2f4bdf1b7

commit 2b6f088ac3acba932b65322e40704bc2f4bdf1b7
Author: Jon Turney <jon.turney@dronecode.org.uk>
Date:   Fri Jul 23 14:57:24 2021 +0100

    newlib: Enable automake silent rules
    
    Use AM_SILENT_RULES, to enable automake silent rules (by default), if we
    are using a version of automake which supports it (>=1.11).
    
    Silent rules can be disabled by configuring with '--disable-silent-rules',
    or invoking 'make V=1'.
    
    For ease of reviewing, this patch doesn't contain configure and
    Makefile.in regeneration.
    
    Future work: There are a few compilations which are not silenced by
    this, as they use custom rules.

Diff:
---
 newlib/README       | 3 +++
 newlib/acinclude.m4 | 1 +
 2 files changed, 4 insertions(+)

diff --git a/newlib/README b/newlib/README
index c82bf8b8c..1c0541284 100644
--- a/newlib/README
+++ b/newlib/README
@@ -127,6 +127,9 @@ directories, you can run `make' on them in parallel (for example, if
 they are NFS-mounted on each of the hosts); they will not interfere
 with each other.
 
+   By default, the execution of build rules in `make' is less verbose.
+To disable, run `make V=1'; or use the `--disable-silent-rules’ option
+of `./configure'.
 
 Specifying names for hosts and targets
 ======================================
diff --git a/newlib/acinclude.m4 b/newlib/acinclude.m4
index 05e545c9f..42af6b548 100644
--- a/newlib/acinclude.m4
+++ b/newlib/acinclude.m4
@@ -121,6 +121,7 @@ AC_SUBST(newlib_basedir)
 AC_CANONICAL_HOST
 
 AM_INIT_AUTOMAKE([cygnus no-define 1.9.5])
+m4_ifdef([AM_SILENT_RULES], [AM_SILENT_RULES(yes)])
 
 # FIXME: We temporarily define our own version of AC_PROG_CC.  This is
 # copied from autoconf 2.12, but does not call AC_PROG_CC_WORKS.  We