Further improvements to error message display for includes

Integrated PR feedback:
- It can be assumed that err is not nil if compiled_chunk is nil (confirmed with the lua docs)
- Check if the file was located before trying to load it, so we can display a descriptive error message with the alternate names that were searched
- Improved the error messages by addubg the file/line information where the include originated, similar to the output of a compiler. The `res` is not output to the error message as in every case it was already part of the error message that was returned and that resulted in very long, repetitive errors

Author: richard-sim

src/base/_foundation.lua

@@ -242,14 +242,16 @@
 		local p5 = path.join(fname, "premake5.lua")
 		local p4 = path.join(fname, "premake4.lua")
 
+		local compiled_chunk
 		local res = os.locate(fname, with_ext, p5, p4)
-		res = res or fname
-		local compiled_chunk, err = loadfile(res)
-		if compiled_chunk == nil then
-			if err then
-				premake.error("Cannot load " .. fname .. ": " .. err)
-			else
-				premake.error("Cannot find either " .. table.implode({fname, with_ext, p5, p4}, "", "", " or "))
+		if res == nil then
+			local caller = filelineinfo(3)
+			premake.error(caller .. ": Cannot find neither " .. table.implode({fname, with_ext, p5, p4}, "", "", " nor "))
+		else
+			compiled_chunk, err = loadfile(res)
+			if err ~= nil then
+				local caller = filelineinfo(3)
+				premake.error(caller .. ": Error loading '" .. fname .. ": " .. err)
 			end
 		end
 		return res, compiled_chunk