ispc: fix build

pkgs/development/compilers/ispc/default.nix

···
     sha256 = "15qi22qvmlx3jrhrf3rwl0y77v66prpan6qb66a55dw3pw2d4jvn";
   };
 
-  enableParallelBuilding = true;
+  enableParallelBuilding = false;
 
   doCheck = true;
 
···
     clang
   ];
 
-  patchPhase = "sed -i -e 's/\\/bin\\///g' -e 's/-lcurses/-lncurses/g' Makefile";
+  # https://github.com/ispc/ispc/pull/1190
+  patches = [ ./gcc5.patch ];
+
+  postPatch = "sed -i -e 's/\\/bin\\///g' -e 's/-lcurses/-lncurses/g' Makefile";
 
   installPhase = ''
     mkdir -p $out/bin

pkgs/development/compilers/ispc/gcc5.patch

···
+diff --git a/cbackend.cpp b/cbackend.cpp
+index 3552205..9c05824 100644
+--- a/cbackend.cpp
++++ b/cbackend.cpp
+@@ -1641,7 +1641,7 @@ void CWriter::printConstant(llvm::Constant *CPV, bool Static) {
+         V = Tmp.convertToDouble();
+       }
+ 
+-      if (isnan(V)) {
++      if (std::isnan(V)) {
+         // The value is NaN
+ 
+         // FIXME the actual NaN bits should be emitted.
+@@ -1665,7 +1665,7 @@ void CWriter::printConstant(llvm::Constant *CPV, bool Static) {
+         else
+           Out << "LLVM_NAN" << (Val == QuietNaN ? "" : "S") << "(\""
+               << Buffer << "\") /*nan*/ ";
+-      } else if (isinf(V)) {
++      } else if (std::isinf(V)) {
+         // The value is Inf
+         if (V < 0) Out << '-';
+         Out << "LLVM_INF" <<