tools/automake: verbose variable compatibility

An old patch attempted to harmonize the way that
both Openwrt and Automake uses the $(V) variable.
However, it was reverted because of the side-effects.

This method is more simple and just
allows Automake to accept any string
as part of the verbosity toggle,
falling back to the default if null.

Ref: e6901bf90 ("tools/automake: Revert "Do not use $(V) - force AM_V=1"")
Ref: 43365ca66 ("Do not use $(V) - force AM_V=1")
Signed-off-by: Michael Pratt <mcpratt@pm.me>

tools/automake/patches/200-other-V-values-for-verbosity.patch

@@ -0,0 +1,59 @@
+From: Bogdan Drozdowski <bogdandr AT op.pl>
+Date: Sat, 31 Dec 2022 20:17:35 +0100
+Subject: [PATCH] Allow other V values for verbosity
+
+---
+ m4/silent.m4    |  2 +-
+ t/silent-gen.sh | 24 ++++++++++++++++++++++++
+ 2 files changed, 25 insertions(+), 1 deletion(-)
+
+--- a/m4/silent.m4
++++ b/m4/silent.m4
+@@ -43,7 +43,7 @@ else
+ fi])
+ if test $am_cv_make_support_nested_variables = yes; then
+   dnl Using '$V' instead of '$(V)' breaks IRIX make.
+-  AM_V='$(V)'
++  AM_V='$(shell if ( test "x$(V)" = "x0" ); then echo 0; elif ( test "x$(V)" = "x" ); then echo $(AM_DEFAULT_VERBOSITY); else echo 1; fi)'
+   AM_DEFAULT_V='$(AM_DEFAULT_VERBOSITY)'
+ else
+   AM_V=$AM_DEFAULT_VERBOSITY
+--- a/t/silent-gen.sh
++++ b/t/silent-gen.sh
+@@ -54,6 +54,18 @@ grep 'cp ' stdout
+ grep 'echo ' stdout
+ 
+ $MAKE clean
++run_make -O V=99
++grep 'GEN ' stdout && exit 1
++grep 'cp ' stdout
++grep 'echo ' stdout
++
++$MAKE clean
++run_make -O V=vvv
++grep 'GEN ' stdout && exit 1
++grep 'cp ' stdout
++grep 'echo ' stdout
++
++$MAKE clean
+ run_make -O V=0
+ grep 'GEN .*foo' stdout
+ grep 'cp ' stdout && exit 1
+@@ -78,5 +90,17 @@ run_make -O V=1
+ grep 'GEN ' stdout && exit 1
+ grep 'cp ' stdout
+ grep 'echo ' stdout
++
++$MAKE clean
++run_make -O V=99
++grep 'GEN ' stdout && exit 1
++grep 'cp ' stdout
++grep 'echo ' stdout
++
++$MAKE clean
++run_make -O V=v
++grep 'GEN ' stdout && exit 1
++grep 'cp ' stdout
++grep 'echo ' stdout
+ 
+ :