modemmanager: Fix build with clang

Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-oe/recipes-connectivity/modemmanager/modemmanager/0001-Do-not-set-Wno-unused-but-set-variable.patch

@@ -0,0 +1,30 @@
+From d4f73b037d11d20f080e74c05df28853fb833075 Mon Sep 17 00:00:00 2001
+From: Khem Raj <raj.khem@gmail.com>
+Date: Fri, 7 Dec 2018 22:59:47 -0800
+Subject: [PATCH] Do not set Wno-unused-but-set-variable
+
+This is gcc specific warning, not implemented by  pretending to be  gcc
+like compilers e.g. clang.
+
+We will pass this option from recipe
+
+Upstream-Status: Inappropriate [OE-Specific]
+
+Signed-off-by: Khem Raj <raj.khem@gmail.com>
+---
+ m4/compiler_warnings.m4 | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/m4/compiler_warnings.m4 b/m4/compiler_warnings.m4
+index f498a28..e65e97f 100644
+--- a/m4/compiler_warnings.m4
++++ b/m4/compiler_warnings.m4
+@@ -11,7 +11,7 @@ if test "$GCC" = "yes" -a "$set_more_warnings" != "no"; then
+ 		      -Wdeclaration-after-statement -Wstrict-prototypes \
+ 		      -Wno-unused-parameter -Wno-sign-compare \
+ 		      -Wno-deprecated-declarations \
+-		      -Wno-unused-but-set-variable -Wformat-security; do
++		      -Wno-unused -Wformat-security; do
+ 		SAVE_CFLAGS="$CFLAGS"
+ 		CFLAGS="$CFLAGS $option"
+ 		AC_MSG_CHECKING([whether gcc understands $option])

meta-oe/recipes-connectivity/modemmanager/modemmanager_1.8.2.bb

@@ -12,6 +12,7 @@ inherit gnomebase gettext systemd vala gobject-introspection bash-completion
 DEPENDS = "glib-2.0 libgudev dbus-glib intltool-native"
 
 SRC_URI = "http://www.freedesktop.org/software/ModemManager/ModemManager-${PV}.tar.xz \
+           file://0001-Do-not-set-Wno-unused-but-set-variable.patch \
            "
 
 SRC_URI[md5sum] = "a49c9f73e46c7b89e5efedda250d22c0"
@@ -33,6 +34,7 @@ PACKAGECONFIG[qmi] = "--with-qmi,--without-qmi,libqmi"
 EXTRA_OECONF = " \
     --with-udev-base-dir=${nonarch_base_libdir}/udev \
 "
+CFLAGS_append_toolchain-gcc = " -Wno-unused-but-set-variable"
 
 FILES_${PN} += " \
     ${datadir}/icons \