Remove legacy windows platform build support

We still support HOST_OS=windows for the SDK host tools cross-builds, but
that's only when USE_MINGW is set when running under linux.

Change-Id: I37da87dc9fbbd69ba10ce4d7f2668ab3f6482d92
diff --git a/core/combo/javac.mk b/core/combo/javac.mk
index fb43ea4..e3838a6 100644
--- a/core/combo/javac.mk
+++ b/core/combo/javac.mk
@@ -26,12 +26,7 @@
 endif
 
 # Whatever compiler is on this system.
-ifeq ($(BUILD_OS), windows)
-    COMMON_JAVAC := development/host/windows/prebuilt/javawrap.exe -J-Xmx256m \
-        $(common_jdk_flags)
-else
-    COMMON_JAVAC := $(JAVACC) -J-Xmx1024M $(common_jdk_flags)
-endif
+COMMON_JAVAC := $(JAVACC) -J-Xmx1024M $(common_jdk_flags)
 
 # Eclipse.
 ifeq ($(CUSTOM_JAVA_COMPILER), eclipse)