refactors optimise check to function premake.config.isoptimizedbuild(flags) which is not local scope as it can be used in other places

adds function premake.config.should_link_incrementally(cfg)
adds new flag NoIncrementalLink

src/base/api.lua

@@ -88,6 +88,7 @@
 				"NoExceptions",
 				"NoFramePointer",
 				"NoImportLib",
+				"NoIncrementalLink",
 				"NoManifest",
 				"NoMinimalRebuild",
 				"NoNativeWChar",

src/base/configs.lua

@@ -15,7 +15,18 @@
 
 	premake.config = { }
 	
+	function premake.config.isoptimizedbuild(flags)
+		return flags.Optimize or flags.OptimizeSize or flags.OptimizeSpeed
+	end
 	
+	function premake.config.should_link_incrementally(cfg)
+		if cfg.kind == "StaticLib" 
+				or premake.config.isoptimizedbuild(cfg.flags)
+				or cfg.flags.NoIncrementalLink then
+			return false
+		end
+		return true
+	end
 -- 
 -- Determine if a configuration represents a "debug" or "release" build.
 -- This controls the runtime library selected for Visual Studio builds

tests/base/test_config.lua

@@ -56,3 +56,27 @@
 		prepare()
 		return test.istrue(premake.config.isdebugbuild(cfg))
 	end
+
+	function suite.shouldIncrementallyLink_staticLib_returnsFalse()
+		kind "StaticLib"
+		prepare()
+		return test.isfalse(premake.config.should_link_incrementally(cfg))
+	end
+	
+	function suite.shouldIncrementallyLink_optimizeFlagSet_returnsFalse()
+		flags { "Optimize" }
+		prepare()
+		return test.isfalse(premake.config.should_link_incrementally(cfg))
+	end
+	
+	function suite.shouldIncrementallyLink_NoIncrementalLinkFlag_returnsFalse()
+		flags { "NoIncrementalLink" }
+		prepare()
+		return test.isfalse(premake.config.should_link_incrementally(cfg))
+	end
+	
+	function suite.shouldIncrementallyLink_notStaticLib_NoIncrementalLinkFlag_noOptimiseFlag_returnsTrue()
+		prepare()
+		return test.istrue(premake.config.should_link_incrementally(cfg))
+	end
+