ensemble-chorus: unpin gcc8

fix build to use default gcc toolchain which fixes link errors
associated with building against mismatched libstd++

patch vendored juice library to remove packed attributes which cause
compile errors but add static asserts to verify that the struct / class
layouts are identical regardless of attribute

pkgs/applications/audio/ensemble-chorus/default.nix

···
     fetchSubmodules = true;
   };
 
+  patches = [
+    # fix compile error regarding packed attribute in 3rd party juice library
+    ./juice-cxx-packing-fix.diff
+  ];
+
   nativeBuildInputs = [ cmake pkg-config ];
 
   buildInputs = [

pkgs/applications/audio/ensemble-chorus/juice-cxx-packing-fix.diff

···
+diff --git a/thirdparty/JUCE/modules/juce_graphics/colour/juce_PixelFormats.h b/thirdparty/JUCE/modules/juce_graphics/colour/juce_PixelFormats.h
+index 69a66e4..3e50635 100644
+--- a/thirdparty/JUCE/modules/juce_graphics/colour/juce_PixelFormats.h
++++ b/thirdparty/JUCE/modules/juce_graphics/colour/juce_PixelFormats.h
+@@ -111,18 +111,10 @@ public:
+     forcedinline uint8 getGreen() const noexcept      { return components.g; }
+     forcedinline uint8 getBlue() const noexcept       { return components.b; }
+ 
+-   #if JUCE_GCC
+-    // NB these are here as a workaround because GCC refuses to bind to packed values.
+-    forcedinline uint8& getAlpha() noexcept           { return comps [indexA]; }
+-    forcedinline uint8& getRed() noexcept             { return comps [indexR]; }
+-    forcedinline uint8& getGreen() noexcept           { return comps [indexG]; }
+-    forcedinline uint8& getBlue() noexcept            { return comps [indexB]; }
+-   #else
+     forcedinline uint8& getAlpha() noexcept           { return components.a; }
+     forcedinline uint8& getRed() noexcept             { return components.r; }
+     forcedinline uint8& getGreen() noexcept           { return components.g; }
+     forcedinline uint8& getBlue() noexcept            { return components.b; }
+-   #endif
+ 
+     //==============================================================================
+     /** Copies another pixel colour over this one.
+@@ -336,21 +328,22 @@ private:
+         uint8 b, g, r, a;
+        #endif
+       #endif
+-    } JUCE_PACKED;
++    };
++
++    // structure must be packed but using the packed attribute causes compile
++    // failures with newer c++ compilers. Verify default packing produces same layout
++    static_assert(sizeof(Components) == 4, "Components struct is not packed");
+ 
+     union
+     {
+         uint32 internal;
+         Components components;
+-       #if JUCE_GCC
+-        uint8 comps[4];  // helper struct needed because gcc does not allow references to packed union members
+-       #endif
+     };
+-}
+-#ifndef DOXYGEN
+- JUCE_PACKED
+-#endif
+-;
++};
++
++// class must be packed but using the packed attribute causes compile
++// failures with newer c++ compilers. Verify default packing produces same layout
++static_assert(sizeof(PixelARGB) == 4, "PixelARGB class is not packed");
+ 
+ 
+ //==============================================================================

pkgs/top-level/all-packages.nix

···
 
   enscript = callPackage ../tools/text/enscript { };
 
-  ensemble-chorus = callPackage ../applications/audio/ensemble-chorus { stdenv = gcc8Stdenv; };
+  ensemble-chorus = callPackage ../applications/audio/ensemble-chorus { };
 
   entr = callPackage ../tools/misc/entr { };