portaudio: fix build for FreeBSD (#387546)

pkgs/development/libraries/portaudio/default.nix

@@ -22,9 +22,12 @@ stdenv.mkDerivation rec {
     pkg-config
     which
   ];
-  buildInputs = [
-    libjack2
-  ] ++ lib.optionals (lib.meta.availableOn stdenv.hostPlatform alsa-lib) [ alsa-lib ];
+  buildInputs =
+    [
+      libjack2
+    ]
+    # Enabling alsa causes linux-only sources to be built
+    ++ lib.optionals stdenv.hostPlatform.isLinux [ alsa-lib ];
 
   configureFlags = [
     "--disable-mac-universal"
@@ -50,7 +53,7 @@ stdenv.mkDerivation rec {
     ''
       make install
     ''
-    + lib.optionalString (lib.meta.availableOn stdenv.hostPlatform alsa-lib) ''
+    + lib.optionalString stdenv.hostPlatform.isLinux ''
       # fixup .pc file to find alsa library
       sed -i "s|-lasound|-L${alsa-lib.out}/lib -lasound|" "$out/lib/pkgconfig/"*.pc
     ''