Add pre-packaged dependency libraries (ESP32-audioI2S and PNGdec)

libraries/PNGdec/linux/Makefile

@@ -0,0 +1,37 @@
+CFLAGS=-D__LINUX__ -Wall -O2 
+LIBS = 
+
+all: png_demo
+
+png_demo: main.o PNGdec.o adler32.o crc32.o infback.o inffast.o inflate.o inftrees.o zutil.o
+	$(CC) main.o PNGdec.o adler32.o crc32.o infback.o inffast.o inflate.o inftrees.o zutil.o $(LIBS) -o png_demo 
+
+main.o: main.cpp
+	$(CXX) $(CFLAGS) -c main.cpp
+
+PNGdec.o: ../src/PNGdec.cpp ../src/png.inl ../src/PNGdec.h
+	$(CXX) $(CFLAGS) -c ../src/PNGdec.cpp
+
+adler32.o: ../src/adler32.c
+	$(CC) $(CFLAGS) -c ../src/adler32.c
+
+crc32.o: ../src/crc32.c
+	$(CC) $(CFLAGS) -c ../src/crc32.c
+
+infback.o: ../src/infback.c
+	$(CC) $(CFLAGS) -c ../src/infback.c
+
+inffast.o: ../src/inffast.c
+	$(CC) $(CFLAGS) -c ../src/inffast.c
+
+inflate.o: ../src/inflate.c
+	$(CC) $(CFLAGS) -c ../src/inflate.c
+
+inftrees.o: ../src/inftrees.c
+	$(CC) $(CFLAGS) -c ../src/inftrees.c
+
+zutil.o: ../src/zutil.c
+	$(CC) $(CFLAGS) -c ../src/zutil.c
+
+clean:
+	rm -rf *.o png_demo