Buildozer Build failed: Couldn't find executable for CC

I run the command --buildozer android debug , because i wan to create a apk file to my phone,but after i reach this point

[INFO]:    Building libffi for armeabi-v7a
**[ERROR]:   Build failed: Couldn't find executable for CC.** This indicates a problem locating the /home/pi/.buildozer/android/platform/android-ndk-r19b/toolchains/llvm/prebuilt/linux-armv7l/bin/clang executable in the Android NDK, not that you don't have a normal compiler installed. Exiting.
Searching path are: '/home/pi/.buildozer/android/platform/android-ndk-r19b/toolchains/llvm/prebuilt/linux-armv7l/bin:/home/pi/.buildozer/android/platform/android-ndk-r19b/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86/bin/:/home/pi/.buildozer/android/platform/android-ndk-r19b/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/:/home/pi/.buildozer/android/platform/android-ndk-r19b:/home/pi/.buildozer/android/platform/android-sdk/tools:/home/pi/.buildozer/android/platform/apache-ant-1.9.4/bin:/usr/bin/jdk-10/bin:/path/to/inflated/jdk-10/bin:/path/to/inflated/jdk-10/bin:/path/to/inflated/jdk-10/bin:/path/to/inflated/jdk-10/bin:/home/pi/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/games:/usr/games'
# Command failed: /usr/bin/python3 -m pythonforandroid.toolchain create --dist_name=myapp --bootstrap=sdl2 --requirements=python3,kivy --arch armeabi-v7a --copy-libs --color=always --storage-dir="/home/pi/Downloads/kivy/MySecApp/.buildozer/android/platform/build-armeabi-v7a" --ndk-api=21
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#     PWD = '/home/pi/Downloads/kivy/MySecApp'
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#     XDG_DATA_DIRS = '/usr/local/share:/usr/share/raspi-ui-overrides:/usr/share:/usr/share/gdm:/var/lib/menu-xdg'
#     PATH = '/home/pi/.buildozer/android/platform/apache-ant-1.9.4/bin:/usr/bin/jdk-10/bin:/path/to/inflated/jdk-10/bin:/path/to/inflated/jdk-10/bin:/path/to/inflated/jdk-10/bin:/path/to/inflated/jdk-10/bin:/home/pi/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/games:/usr/games'
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#     ANDROIDAPI = '27'
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# 
# Buildozer failed to execute the last command
# The error might be hidden in the log above this error
# Please read the full log, and search for it before
# raising an issue with buildozer itself.
# In case of a bug report, please add a full log with log_level = 2

It showing this Build failed: Couldn't find executable for CC. error . Why seems to be the problem here? Any help will be appreciated , thanks!

from Buildozer Build failed: Couldn't find executable for CC