add use_default_cc_compiler methods

gem.spec

@@ -1,7 +1,7 @@
 Gem::Specification.new do |s|
   s.name        = 'mkmf-cu'
-  s.version     = '0.1.1'
-  s.date        = '2016-02-24'
+  s.version     = '0.1.2.pre2'
+  s.date        = '2016-03-26'
   s.summary     = "Write Ruby extension in C/C++ with NVIDIA CUDA."
   s.description =
   "Write Ruby extension in C/C++ with NVIDIA CUDA. A simple wrapper command for nvcc and a monkey patch for mkmf."

lib/mkmf-cu.rb

@@ -6,12 +6,22 @@
 MakeMakefile::C_EXT << "cu"
 MakeMakefile::SRC_EXT << "cu"
 
-def compile_cu_with_cxx_compiler
+def treat_cu_as_cxx
   MakeMakefile::C_EXT.delete("cu")
   MakeMakefile::CXX_EXT << "cu"
 end
 
-def compile_cu_with_cc_compiler
+def treat_cu_as_cc
   MakeMakefile::CXX_EXT.delete("cu")
   MakeMakefile::C_EXT << "cu"
 end
+
+def use_default_cc_compiler
+  MakeMakefile::CONFIG["CC"] = RbConfig::CONFIG["CC"]
+  MakeMakefile::C_EXT.delete("cu")
+end
+
+def use_default_cxx_compiler
+  MakeMakefile::CONFIG["CXX"] = RbConfig::CONFIG["CXX"]
+  MakeMakefile::CXX_EXT.delete("cu")
+end

test/test_mkmf-cu.rb

@@ -59,7 +59,7 @@ def test_mkmf_cu
     assert MakeMakefile::C_EXT.include?("cu")
     assert MakeMakefile::SRC_EXT.include?("cu")
 
-    compile_cu_with_cxx_compiler()
+    treat_cu_as_cxx()
     assert !MakeMakefile::C_EXT.include?("cu")
     assert MakeMakefile::CXX_EXT.include?("cu")
   end