In Android.mk, how to copy all the files in a directory recursively to out/vendor/ directory

Question

I have a folder structure as following.

sdk
├── 1.txt
├── 2.txt
└── install
    ├── bin
    │   └── 3.txt
    └── lib
        └── 4.txt

I want to copy all these files to vendor/etc/ using Android.mk.


My sample Android.mk code:

SDK_SRC_DIR = sdk

PRODUCT_COPY_FILES += \
        $(foreach f,$(wildcard $(SDK_SRC_DIR)/*/*),$(f):$(subst $(SDK_SRC_DIR),$(TARGET_COPY_OUT_VENDOR)/etc/,$(f)))

I get an error as following while building.

[ 3% 1/31] Copy: out/target/product/hikey960/vendor/sdk/install/bin
FAILED: out/target/product/hikey960/vendor/sdk/install/bin
/bin/bash -c "(rm -f out/target/product/hikey960/vendor/sdk/install/bin ) && (cp \"sdk/install/bin\" \"out/target/product/hikey960/vendor/sdk/install/bin\" )"

cp: omitting directory 'sdk/install/bin'

[ 6% 2/31] Copy: out/target/product/hikey960/vendor/sdk/install/lib
FAILED: out/target/product/hikey960/vendor/sdk/install/lib
/bin/bash -c "(rm -f out/target/product/hikey960/vendor/sdk/install/lib ) && (cp \"sdk/install/lib\" \"out/target/product/hikey960/vendor/sdk/install/lib\" )"

cp: omitting directory 'sdk/install/lib'

So how to copy properly?