Use macro for Python 2 interpreter

Use proper export and quoting

mozjs52.spec

@@ -7,7 +7,7 @@
 
 Name:           mozjs%{major}
 Version:        52.5.0
-Release:        1%{?dist}
+Release:        2%{?dist}
 Summary:        SpiderMonkey JavaScript library
 
 License:        MPLv2.0 and MPLv1.1 and BSD and GPLv2+ and GPLv3+ and LGPLv2.1 and LGPLv2.1+ and AFL and ASL 2.0
@@ -81,9 +81,9 @@ rm -rf ../../modules/zlib
 %build
 # Disable null pointer gcc6 optimization in gcc6 (rhbz#1328045)
 export CFLAGS="%{optflags} -fno-tree-vrp -fno-strict-aliasing -fno-delete-null-pointer-checks"
-export CXXFLAGS=$CFLAGS
-LINKFLAGS="%{?__global_ldflags}"
-export PYTHON=/usr/bin/python2
+export CXXFLAGS="$CFLAGS"
+export LINKFLAGS="%{?__global_ldflags}"
+export PYTHON="%{__python2}"
 
 autoconf-2.13
 %configure \
@@ -160,6 +160,10 @@ jit-test/jit_test.py -s -t 1800 --no-progress ../../js/src/js/src/shell/js basic
 %{_includedir}/mozjs-%{major}/
 
 %changelog
+* Fri Nov 24 2017 Björn Esser <besser82@fedoraproject.org> - 52.5.0-2
+- Use macro for Python 2 interpreter
+- Use proper export and quoting
+
 * Tue Nov 14 2017 Kalev Lember <klember@redhat.com> - 52.5.0-1
 - Update to 52.5.0