Fix installation on jruby (#5)

Author: comandeo-mongo

ext/libmongocrypt/extconf.rb

@@ -45,10 +45,10 @@
   system(MAKE)
 end
 
-lib_file_extension = case RUBY_PLATFORM
+lib_file_extension = case RbConfig::CONFIG['target_os']
                      when /linux/ then "so"
                      when /darwin/ then "dylib"
-                     else abort "ERROR: this gem supports only linux and macos"
+                     else abort "ERROR: this gem supports only linux and macos, #{RbConfig::CONFIG['target_os']} is not supported"
                      end
 
 lib_file = File.join(build_dir, "#{extension_name}.#{lib_file_extension}")

lib/libmongocrypt_helper.rb

@@ -3,10 +3,10 @@
 module LibmongocryptHelper
   def libmongocrypt_path
     @libmongocrypt_path ||= begin
-      lib_file_extension = case RUBY_PLATFORM
+      lib_file_extension = case RbConfig::CONFIG['target_os']
       when /linux/ then "so"
       when /darwin/ then "dylib"
-      else raise "ERROR: this gem supports only linux and macos"
+      else raise "ERROR: this gem supports only linux and macos, #{RbConfig::CONFIG['target_os']} is not supported"
       end
 
       File.join(

lib/libmongocrypt_helper/version.rb

@@ -1,5 +1,5 @@
 module LibmongocryptHelper
-  VERSION = '1.7.4.0.1001'
+  VERSION = '1.7.4.0.1002'
 
   LIBMONGOCRYPT_VERSION = '1.7.4'
 end