Fixing Android build from Linux. Letting ANDROID_NDK to be modified at compile time. Default path to the ANDROID_TOOLCHAIN have changed in the latest Android command-line tools release. (#1264)

Co-authored-by: Branlix 3000 <branlix@3000.3k>

src/Makefile

@@ -168,8 +168,8 @@ ifeq ($(PLATFORM),PLATFORM_ANDROID)
         ANDROID_NDK = C:/android-ndk-r21
         ANDROID_TOOLCHAIN = $(ANDROID_NDK)/toolchains/llvm/prebuilt/windows-x86_64
     else
-        ANDROID_NDK = /usr/lib/android/ndk
-        ANDROID_TOOLCHAIN = $(ANDROID_NDK)/toolchains/llvm/prebuilt/linux
+        ANDROID_NDK ?= /usr/lib/android/ndk
+        ANDROID_TOOLCHAIN = $(ANDROID_NDK)/toolchains/llvm/prebuilt/linux-x86_64
     endif
 
     ifeq ($(ANDROID_ARCH),ARM)