helm: fix #79177 on linux (#137146)

* helm: replace /usr/share reference with $out/share

with the stock path helm will always determine that it is not installed
properly and thus refuse to save/load settings, preset and builtin presets.

* helm: remove buildPhase

the default is adequate since using `make install` during installPhase will
build the remaining targets anyway.

* helm: enable parallel builds

* helm: fix package lints

pkgs/applications/audio/helm/default.nix

@@ -26,10 +26,13 @@
   buildInputs = [
     xorg.libX11 xorg.libXcomposite xorg.libXcursor xorg.libXext
     xorg.libXinerama xorg.libXrender xorg.libXrandr
-    freetype alsa-lib curl libjack2 pkg-config libGLU libGL lv2
+    freetype alsa-lib curl libjack2 libGLU libGL lv2
   ];
+  nativeBuildInputs = [ pkg-config ];
 
   CXXFLAGS = "-DHAVE_LROUND";
+  enableParallelBuilding = true;
+  makeFlags = [ "DESTDIR=$(out)" ];
 
   patches = [
     # gcc9 compatibility https://github.com/mtytel/helm/pull/233
@@ -41,15 +44,7 @@
 
   prePatch = ''
     sed -i 's|usr/||g' Makefile
-  '';
-
-  buildPhase = ''
-    make lv2
-    make standalone
-  '';
-
-  installPhase = ''
-   make DESTDIR="$out" install
+    sed -i "s|/usr/share/|$out/share/|" src/common/load_save.cpp
   '';
 
   meta = with lib; {
@@ -72,7 +67,7 @@
         Simple arpeggiator
         Effects: Formant filter, stutter, delay
     '';
-    license = lib.licenses.gpl3;
+    license = lib.licenses.gpl3Plus;
     maintainers = [ maintainers.magnetophon ];
     platforms = platforms.linux;
   };