Should need to know its C++ compiler, too

curl/curl.spec

@@ -61,6 +61,7 @@ AutoReqProv:  no
 %build
     echo 'ac_cv_header_openssl_engine_h=no' >config.cache
     CC="%{l_cc}" \
+    CXX="%{l_cxx}" \
     CFLAGS="%{l_cflags -O} %{l_cppflags}" \
     CPPFLAGS="%{l_cppflags}" \
     LDFLAGS="%{l_ldflags}" \