mkmf.rb: avoid interference

* lib/mkmf.rb (try_cppflags, try_cflags, try_ldflags): get rid of
  interference by modifying global variables in have_devel? method.
  [ruby-core:67962] [Bug #10821]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49482 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 3 insertions, 9 deletions

diff --git a/lib/mkmf.rb b/lib/mkmf.rb
index e8750e4f9d..67af386bfa 100644
--- a/lib/mkmf.rb
+++ b/lib/mkmf.rb
@@ -610,9 +610,7 @@ MSG
   end
 
   def try_cppflags(flags)
-    with_cppflags(flags) do
-      try_header("int main() {return 0;}")
-    end
+    try_header(MAIN_DOES_NOTHING, flags)
   end
 
   def with_cflags(flags)
@@ -624,9 +622,7 @@ MSG
   end
 
   def try_cflags(flags)
-    with_cflags(flags) do
-      try_compile("int main() {return 0;}")
-    end
+    try_compile(MAIN_DOES_NOTHING, flags)
   end
 
   def with_ldflags(flags)
@@ -638,9 +634,7 @@ MSG
   end
 
   def try_ldflags(flags)
-    with_ldflags(flags) do
-      try_link("int main() {return 0;}")
-    end
+    try_link(MAIN_DOES_NOTHING, flags)
   end
 
   def try_static_assert(expr, headers = nil, opt = "", &b)