remove unneeded CXX, since we are not using C++ at all

libxslt/libxslt.spec

@@ -66,7 +66,6 @@ AutoReqProv:  no
 
 %build
     CC="%{l_cc}" \
-    CXX="%{l_cxx}" \
     CFLAGS="%{l_cflags -O} %{l_cppflags}" \
     CPPFLAGS="%{l_cppflags}" \
     LDFLAGS="%{l_ldflags}" \