netcdf: fix tests on Linux

`nczarr_test/Makefile.am` prepends new shebang lines to the start of
some tests when they are built, which breaks tests on Linux because
`/bin/bash` does not exist.

pkgs/development/libraries/netcdf/default.nix

@@ -30,6 +30,10 @@ in stdenv.mkDerivation rec {
     for a in ncdap_test/Makefile.am ncdap_test/Makefile.in; do
       substituteInPlace $a --replace testurl.sh " "
     done
+
+    # Prevent building the tests from prepending `#!/bin/bash` and wiping out the patched shenbangs.
+    substituteInPlace nczarr_test/Makefile.in \
+      --replace '#!/bin/bash' '${stdenv.shell}'
   '';
 
   nativeBuildInputs = [ m4 removeReferencesTo ];