[build, Android] libjpeg-turbo: make sure to copy the right lib (#769)

Forgot to push this, so koreader/koreader#4352
was incomplete.

Cf. #768

Makefile.defs

@@ -552,7 +552,7 @@ HARFBUZZ_LIB=$(OUTPUT_DIR)/libs/libharfbuzz$(HARFBUZZ_LIB_EXT)
 HARFBUZZ_BUILD_DIR=$(THIRDPARTY_DIR)/harfbuzz/build/$(MACHINE)
 HARFBUZZ_DIR=$(CURDIR)/$(HARFBUZZ_BUILD_DIR)/harfbuzz-prefix/src/harfbuzz-build
 
-JPEG_LIB_EXT=$(if $(WIN32),-8.dll,$(if $(DARWIN),.8.dylib,.so$(if $(ANDROID),,.8)))
+JPEG_LIB_EXT=$(if $(WIN32),-8.dll,$(if $(DARWIN),.8.dylib,.so.8))
 JPEG_LIB=$(OUTPUT_DIR)/libs/libjpeg$(JPEG_LIB_EXT)
 TURBOJPEG_LIB=$(OUTPUT_DIR)/libs/libturbojpeg$(if $(WIN32),.dll,$(if $(DARWIN),.dylib,.so))
 JPEG_BUILD_DIR=$(THIRDPARTY_DIR)/libjpeg-turbo/build/$(MACHINE)