treewide: avoid fatal warnings from gcc7

pkgs/development/compilers/openjdk/7.nix

@@ -69,7 +69,10 @@ let
         fontconfig perl file bootjdk
       ];
 
-    NIX_CFLAGS_COMPILE = "-Wno-error=deprecated-declarations";
+    NIX_CFLAGS_COMPILE = [
+      "-Wno-error=deprecated-declarations"
+      "-Wno-error=format-overflow" # newly detected by gcc7
+    ];
 
     NIX_LDFLAGS = if minimal then null else "-lfontconfig -lXcursor -lXinerama";
 

pkgs/development/libraries/libwps/default.nix

@@ -12,6 +12,8 @@ stdenv.mkDerivation rec {
   nativeBuildInputs = [ pkgconfig ];
   buildInputs = [ boost librevenge zlib ];
 
+  NIX_CFLAGS_COMPILE = [ "-Wno-error=implicit-fallthrough" ]; # newly detected by gcc-7
+
   meta = with stdenv.lib; {
     homepage = http://libwps.sourceforge.net/;
     description = "Microsoft Works document format import filter library";

pkgs/development/libraries/usbredir/default.nix

@@ -10,7 +10,8 @@ stdenv.mkDerivation rec {
   };
 
   # Works around bunch of "format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'uint64_t {aka long long unsigned int}'" warnings
-  NIX_CFLAGS_COMPILE = stdenv.lib.optionalString (!stdenv.is64bit) "-Wno-error=format";
+  NIX_CFLAGS_COMPILE = stdenv.lib.optional (!stdenv.is64bit) "-Wno-error=format"
+    ++ [ "-Wno-error=format-truncation" ]; # newly detected with gcc-7
 
   nativeBuildInputs = [ pkgconfig ];
   buildInputs = [ libusb ];