treewide: NIX_*_COMPILE -> string

pkgs/applications/graphics/gimp/plugins/default.nix

@@ -48,7 +48,7 @@ stdenv.lib.makeScope pkgs.newScope (self: with self; {
       url = https://ftp.gimp.org/pub/gimp/plug-ins/v2.6/gap/gimp-gap-2.6.0.tar.bz2;
       sha256 = "1jic7ixcmsn4kx2cn32nc5087rk6g8xsrz022xy11yfmgvhzb0ql";
     };
-    NIX_LDFLAGS = [ "-lm" ];
+    NIX_LDFLAGS = "-lm";
     patchPhase = ''
       sed -e 's,^\(GIMP_PLUGIN_DIR=\).*,\1'"$out/${gimp.name}-plugins", \
        -e 's,^\(GIMP_DATA_DIR=\).*,\1'"$out/share/${gimp.name}", -i configure
@@ -141,7 +141,7 @@ stdenv.lib.makeScope pkgs.newScope (self: with self; {
       Filters/Enhance/Wavelet sharpen
     */
     name = "wavelet-sharpen-0.1.2";
-    NIX_LDFLAGS = [ "-lm" ];
+    NIX_LDFLAGS = "-lm";
     src = fetchurl {
       url = http://registry.gimp.org/files/wavelet-sharpen-0.1.2.tar.gz;
       sha256 = "0vql1k67i21g5ivaa1jh56rg427m0icrkpryrhg75nscpirfxxqw";