numpy: fix on musl

pkgs/development/python-modules/numpy/default.nix

@@ -1,4 +1,4 @@
-{lib, fetchPypi, python, buildPythonPackage, isPy27, isPyPy, gfortran, nose, blas}:
+{lib, fetchPypi, python, buildPythonPackage, isPy27, isPyPy, gfortran, nose, blas, hostPlatform }:
 
 buildPythonPackage rec {
   pname = "numpy";
@@ -20,6 +20,18 @@ buildPythonPackage rec {
     ./numpy-distutils-C++.patch
   ];
 
+  postPatch = lib.optionalString hostPlatform.isMusl ''
+    # Use fenv.h
+    sed -i \
+      numpy/core/src/npymath/ieee754.c.src \
+      numpy/core/include/numpy/ufuncobject.h \
+      -e 's/__GLIBC__/__linux__/'
+    # Don't use various complex trig functions
+    substituteInPlace numpy/core/src/private/npy_config.h \
+      --replace '#if defined(__GLIBC__)' "#if 1" \
+      --replace '#if !__GLIBC_PREREQ(2, 18)' "#if 1"
+  '';
+
   preConfigure = ''
     sed -i 's/-faltivec//' numpy/distutils/system_info.py
     export NPY_NUM_BUILD_JOBS=$NIX_BUILD_CORES