Move sh selection out of GUI makefile

* The TWRP_SH_TARGET variable is only used if TW_USE_TOOLBOX == false,
  so it doesn't really need to be defined.
* Move the busybox sh symlink creation nearer to the toolbox/busybox
  build rules and take advantage of LOCAL_POST_INSTALL_CMD which has
  been around since Android 4.3.

Change-Id: I7850f9c3e113d43ad519dd5c9a7d25e36ec1c426

Android.mk

@@ -380,6 +380,11 @@ else
 endif
 ifneq ($(TW_USE_TOOLBOX), true)
     LOCAL_ADDITIONAL_DEPENDENCIES += busybox_symlinks
+    ifeq ($(shell test $(PLATFORM_SDK_VERSION) -lt 24; echo $$?),0)
+        LOCAL_POST_INSTALL_CMD := \
+            $(hide) mkdir -p $(TARGET_RECOVERY_ROOT_OUT)/sbin && \
+            ln -sf /sbin/busybox $(TARGET_RECOVERY_ROOT_OUT)/sbin/sh
+    endif
 else
     ifneq ($(wildcard external/toybox/Android.mk),)
         LOCAL_ADDITIONAL_DEPENDENCIES += toybox_symlinks
@@ -391,6 +396,7 @@ else
         LOCAL_ADDITIONAL_DEPENDENCIES += unzip
     endif
 endif
+
 ifneq ($(TW_NO_EXFAT), true)
     LOCAL_ADDITIONAL_DEPENDENCIES += mkexfatfs fsckexfat
     ifneq ($(TW_NO_EXFAT_FUSE), true)

gui/Android.mk

@@ -141,22 +141,11 @@ endif
 TWRP_RES += $(TW_ADDITIONAL_RES)
 
 TWRP_RES_GEN := $(intermediates)/twrp
-ifneq ($(TW_USE_TOOLBOX), true)
-    TWRP_SH_TARGET := /sbin/busybox
-else
-    TWRP_SH_TARGET := /sbin/mksh
-endif
-
 $(TWRP_RES_GEN):
 	mkdir -p $(TARGET_RECOVERY_ROOT_OUT)$(TWRES_PATH)
 	cp -fr $(TWRP_RES) $(TARGET_RECOVERY_ROOT_OUT)$(TWRES_PATH)
 	cp -fr $(TWRP_THEME_LOC)/* $(TARGET_RECOVERY_ROOT_OUT)$(TWRES_PATH)
 	mkdir -p $(TARGET_RECOVERY_ROOT_OUT)/sbin/
-ifneq ($(TW_USE_TOOLBOX), true)
-ifeq ($(shell test $(PLATFORM_SDK_VERSION) -lt 24; echo $$?),0)
-	ln -sf $(TWRP_SH_TARGET) $(TARGET_RECOVERY_ROOT_OUT)/sbin/sh
-endif
-endif
 
 LOCAL_GENERATED_SOURCES := $(TWRP_RES_GEN)
 LOCAL_SRC_FILES := twrp $(TWRP_RES_GEN)