FT_Get_Var error on compiling

[Julian@julian-linux-t450 gtk]$ gcc `pkg-config --cflags gtk+-3.0` -o exam00 exam00.c `pkg-config --libs gtk+-3.0` 
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libcairo.so: undefined reference to `FT_Get_Var_Design_Coordinates'
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../lib64/libcairo.so: undefined reference to `FT_Get_Var_Blend_Coordinates'

ldd /usr/lib64/libcairo.so

we can find freetype lib links to a strange location

[Julian@julian-linux-t450 gtk]$ ldd /usr/lib64/libcairo.so
        linux-vdso.so.1 =>  (0x00007ffe0ed48000)
        libpthread.so.0 => /lib64/libpthread.so.0 (0x00007ff1a7633000)
        libpixman-1.so.0 => /lib64/libpixman-1.so.0 (0x00007ff1a738a000)
        libfontconfig.so.1 => /lib64/libfontconfig.so.1 (0x00007ff1a7148000)
        libfreetype.so.6 => /usr/lib64/freetype-infinality/libfreetype.so.6 (0x00007ff1a6e9b000)

add -lfreetype can resolve this issue

[Julian@julian-linux-t450 gtk]$ gcc `pkg-config --cflags gtk+-3.0` -o exam00 exam00.c `pkg-config --libs gtk+-3.0` -lfreetype
[Julian@julian-linux-t450 gtk]$