Test added for reading BuildProperties from ./platform.sketch.txt file

test/sketch_with_platform_sketch_txt/platform.sketch.txt

@@ -0,0 +1,2 @@
+compiler.c.extra_flags   = -DSKETCH_DEFINED_VALUE=1
+compiler.cpp.extra_flags = -DSKETCH_DEFINED_VALUE=2

test/sketch_with_platform_sketch_txt/sketch_with_platform_sketch_txt.ino

@@ -0,0 +1,6 @@
+#ifndef SKETCH_DEFINED_VALUE
+	#error SKETCH_DEFINED_VALUE was not defined in ./platform.sketch.txt
+#endif
+
+void setup() {}
+void loop() {}

test/try_build_of_problematic_sketch_test.go

@@ -31,11 +31,12 @@
 package test
 
 import (
-	"github.com/arduino/arduino-builder"
-	"github.com/arduino/arduino-builder/types"
 	"os"
 	"path/filepath"
 	"testing"
+
+	"github.com/arduino/arduino-builder"
+	"github.com/arduino/arduino-builder/types"
 )
 
 func TestTryBuild001(t *testing.T) {
@@ -217,6 +218,10 @@ func TestTryBuild042(t *testing.T) {
 	tryBuild(t, "sketch_with_fake_function_pointer", "sketch_with_fake_function_pointer.ino")
 }
 
+func TestTryBuild043(t *testing.T) {
+	tryBuild(t, "sketch_with_platform_sketch_txt", "sketch_with_platform_sketch_txt.ino")
+}
+
 func makeDefaultContext(t *testing.T) *types.Context {
 	DownloadCoresAndToolsAndLibraries(t)