Fix prebuilts for target builds with USE_MINGW=1.

USE_MINGW=1 mm didn't work in directories that contained target modules
because the build system would use the Windows locations and extensions
when trying to find the host GCC prebuilts. Windows is the target OS,
not the OS we're building from.

Change-Id: Ic994fed15388d0c7d393f71ba28fe7afdc659f5c
diff --git a/core/combo/TARGET_linux-mips64.mk b/core/combo/TARGET_linux-mips64.mk
index b34b7a6..1116f46 100644
--- a/core/combo/TARGET_linux-mips64.mk
+++ b/core/combo/TARGET_linux-mips64.mk
@@ -57,13 +57,13 @@
 TARGET_TOOLS_PREFIX := $(TARGET_TOOLCHAIN_ROOT)/bin/mips64el-linux-android-
 endif
 
-TARGET_CC := $(TARGET_TOOLS_PREFIX)gcc$(HOST_EXECUTABLE_SUFFIX)
-TARGET_CXX := $(TARGET_TOOLS_PREFIX)g++$(HOST_EXECUTABLE_SUFFIX)
-TARGET_AR := $(TARGET_TOOLS_PREFIX)ar$(HOST_EXECUTABLE_SUFFIX)
-TARGET_OBJCOPY := $(TARGET_TOOLS_PREFIX)objcopy$(HOST_EXECUTABLE_SUFFIX)
-TARGET_LD := $(TARGET_TOOLS_PREFIX)ld$(HOST_EXECUTABLE_SUFFIX)
-TARGET_READELF := $(TARGET_TOOLS_PREFIX)readelf$(HOST_EXECUTABLE_SUFFIX)
-TARGET_STRIP := $(TARGET_TOOLS_PREFIX)strip$(HOST_EXECUTABLE_SUFFIX)
+TARGET_CC := $(TARGET_TOOLS_PREFIX)gcc
+TARGET_CXX := $(TARGET_TOOLS_PREFIX)g++
+TARGET_AR := $(TARGET_TOOLS_PREFIX)ar
+TARGET_OBJCOPY := $(TARGET_TOOLS_PREFIX)objcopy
+TARGET_LD := $(TARGET_TOOLS_PREFIX)ld
+TARGET_READELF := $(TARGET_TOOLS_PREFIX)readelf
+TARGET_STRIP := $(TARGET_TOOLS_PREFIX)strip
 
 TARGET_NO_UNDEFINED_LDFLAGS := -Wl,--no-undefined