*: fix builds by disregarding warning from new glibc

Also, in case of collectd, the -lgcc_s shouldn't be needed anymore,
as the library is in ${glibc}/lib/ now, which is practically always on RPATH.

In case of seyren it was some stdenv change uncovering the mistake of
putting src into buildInputs.

pkgs/applications/networking/browsers/netsurf/libsvgtiny.nix

@@ -7,6 +7,8 @@ stdenv.mkDerivation {
                (fetchurl { url = "http://mawercer.de/~nix/repos/libsvgtiny-9721.tar.gz"; sha256 = "0c4c8e357c220218a32ef789eb2ba8226a403d4c2b550d7c65f351a0af5d1a71"; });
   # END
 
+  NIX_CFLAGS_COMPILE = "-Wno-error=cpp";
+
   installPhase = "make PREFIX=$out install";
   buildInputs = [pkgconfig gperf libxml2];