libpsl: make python both a build and runtime dependency

Previously, python3 was only provided as a nativeBuildInput. However,
libpsl.bin distributes python scripts. To make them use the right
python, provide python as a buildInput and specify which python to
use at build time with a configure flag.

pkgs/development/libraries/libpsl/default.nix

@@ -10,6 +10,7 @@
 , libxslt
 , pkg-config
 , python3
+, buildPackages
 , valgrind
 , publicsuffix-list
 }:
@@ -33,14 +34,14 @@ stdenv.mkDerivation rec {
     gtk-doc
     lzip
     pkg-config
-    python3
     libxslt
   ];
 
   buildInputs = [
     libidn2
     libunistring
     libxslt
+    python3
   ];
 
   propagatedBuildInputs = [
@@ -61,6 +62,7 @@ stdenv.mkDerivation rec {
     "--with-psl-distfile=${publicsuffix-list}/share/publicsuffix/public_suffix_list.dat"
     "--with-psl-file=${publicsuffix-list}/share/publicsuffix/public_suffix_list.dat"
     "--with-psl-testfile=${publicsuffix-list}/share/publicsuffix/test_psl.txt"
+    "PYTHON=${lib.getExe buildPackages.python3}"
   ];
 
   enableParallelBuilding = true;