dev-db/unixODBC: build w/ -std=gnu17

The custom bool in something pg is a bit suspicious as pg upstream
fixed a similar problem but I haven't looked into it.

Closes: https://bugs.gentoo.org/947922
Signed-off-by: Sam James <sam@gentoo.org>

dev-db/unixODBC/unixODBC-2.3.12-r1.ebuild

@@ -3,7 +3,7 @@
 
 EAPI=8
 
-inherit autotools multilib-minimal
+inherit autotools flag-o-matic multilib-minimal
 
 DESCRIPTION="Complete ODBC driver manager"
 HOMEPAGE="https://www.unixodbc.org/"
@@ -45,6 +45,9 @@ multilib_src_configure() {
 	export LEX=flex
 	unset YACC
 
+	# bug #947922
+	append-cflags -std=gnu17
+
 	# --enable-driver-conf is --enable-driverc as per configure.in
 	local myeconfargs=(
 		--cache-file="${BUILD_DIR}"/config.cache