try different name

Author: kalbasit

ext/proj4_c_impl/extconf.rb

@@ -12,11 +12,11 @@
 
   require "mkmf"
 
-  with_system_headers = with_config("system-headers", default = true)
-  with_system_libs = with_config("system-libs", default = true)
+  with_default_header_paths = with_config("default-header-paths", default = true)
+  with_default_lib_paths = with_config("default-lib-paths", default = true)
 
   header_dirs_ = [ ::RbConfig::CONFIG["includedir"] ]
-  if with_system_headers
+  if with_default_header_paths
     header_dirs_.push(
       "/usr/local/include",
       "/usr/local/proj/include",
@@ -31,7 +31,7 @@
   end
 
   lib_dirs_ = [ ::RbConfig::CONFIG["libdir"] ]
-  if with_system_libs
+  if with_default_lib_paths
     lib_dirs_.push(
       "/usr/local/lib",
       "/usr/local/lib64",