executing my code gives  symbol lookup error undefined symbol: glad_glGenTextures
on executing my code I am facing this error
`./sample2D: symbol lookup error: /usr/local/lib/libftgl.so.2: undefined symbol: glad_glGenTextures`

```
all: sample2D

sample2D: Sample_GL3_2D.cpp glad.c
        g++ -o sample2D Sample_GL3_2D.cpp glad.c -lGL -lglfw -lGLU -lftgl -ldl -std=c++11

clean:
        rm sample2D

```

this is my Makefile
