Undefined reference when linking to .a library - c++

Question

I'm trying out this library:
https://github.com/dacap/clip
I've git-cloned it, then built it using the following:
cmake .
make
This produces a library called libclip.a.
Now, I've taken the sample Hello World code, which is this:
#include "clip/clip.h"
int main() {
clip::set_text("Hello World");
}
Given that the above is in a file called cliptest2.cpp, I compile it as follows:
g++ -lclip cliptest2.cpp -o cliptest2
Every time, I get the following:
/usr/bin/ld: /tmp/cc71SQmy.o: in function `main':
cliptest2.cpp:(.text+0x47): undefined reference to `clip::set_text(std::__cxx11::basic_string<char, std::char_traits, std::allocator > const&)'
collect2: error: ld returned 1 exit status
I do understand how the linker works and have gone through dozens of other questions with similar errors. However, given that I am building the third party library and linking it into my sample program, I don't understand why the set_text() method is not being resolved.
Edit: I've tried a few things, also as a result of the comments below. The source code for the clip library resides at ~/git/clip, and I am compiling cliptest2.cpp from the home directory itself. Therefore, adjusting the command suggested by #MathiasSchmid to my environment, I end up with this:
g++ cliptest2.cpp -I git -L git/clip -lclip -lxcb -lpthread -o cliptest2
I run this on my Kubuntu 20.04 LTS, and get all the following errors:
daniel#orion:~$ g++ cliptest2.cpp -I git -L git/clip -lclip -lxcb -lpthread -o cliptest2
/usr/bin/ld: git/clip/libclip.a(clip_x11.cpp.o): in function `clip::x11::write_data_fn(png_struct_def*, unsigned char*, unsigned long)':
clip_x11.cpp:(.text+0x4f): undefined reference to `png_get_io_ptr'
/usr/bin/ld: git/clip/libclip.a(clip_x11.cpp.o): in function `clip::x11::write_png(clip::image const&, std::vector<unsigned char, std::allocator<unsigned char> >&)':
clip_x11.cpp:(.text+0x117): undefined reference to `png_create_write_struct'
/usr/bin/ld: clip_x11.cpp:(.text+0x13a): undefined reference to `png_create_info_struct'
/usr/bin/ld: clip_x11.cpp:(.text+0x158): undefined reference to `png_destroy_write_struct'
/usr/bin/ld: clip_x11.cpp:(.text+0x17d): undefined reference to `png_set_longjmp_fn'
/usr/bin/ld: clip_x11.cpp:(.text+0x1a5): undefined reference to `png_destroy_write_struct'
/usr/bin/ld: clip_x11.cpp:(.text+0x1cb): undefined reference to `png_set_write_fn'
/usr/bin/ld: clip_x11.cpp:(.text+0x232): undefined reference to `png_set_IHDR'
/usr/bin/ld: clip_x11.cpp:(.text+0x249): undefined reference to `png_write_info'
/usr/bin/ld: clip_x11.cpp:(.text+0x255): undefined reference to `png_set_packing'
/usr/bin/ld: clip_x11.cpp:(.text+0x268): undefined reference to `png_get_rowbytes'
/usr/bin/ld: clip_x11.cpp:(.text+0x27a): undefined reference to `png_malloc'
/usr/bin/ld: clip_x11.cpp:(.text+0x3cd): undefined reference to `png_write_rows'
/usr/bin/ld: clip_x11.cpp:(.text+0x3e9): undefined reference to `png_free'
/usr/bin/ld: clip_x11.cpp:(.text+0x3fc): undefined reference to `png_write_end'
/usr/bin/ld: clip_x11.cpp:(.text+0x40f): undefined reference to `png_destroy_write_struct'
/usr/bin/ld: git/clip/libclip.a(clip_x11.cpp.o): in function `clip::x11::read_data_fn(png_struct_def*, unsigned char*, unsigned long)':
clip_x11.cpp:(.text+0x45d): undefined reference to `png_get_io_ptr'
/usr/bin/ld: git/clip/libclip.a(clip_x11.cpp.o): in function `clip::x11::read_png(unsigned char const*, unsigned long, clip::image*, clip::image_spec*)':
clip_x11.cpp:(.text+0x575): undefined reference to `png_create_read_struct'
/usr/bin/ld: clip_x11.cpp:(.text+0x5a1): undefined reference to `png_create_info_struct'
/usr/bin/ld: clip_x11.cpp:(.text+0x5cd): undefined reference to `png_destroy_read_struct'
/usr/bin/ld: clip_x11.cpp:(.text+0x5f5): undefined reference to `png_set_longjmp_fn'
/usr/bin/ld: clip_x11.cpp:(.text+0x628): undefined reference to `png_destroy_read_struct'
/usr/bin/ld: clip_x11.cpp:(.text+0x68f): undefined reference to `png_set_read_fn'
/usr/bin/ld: clip_x11.cpp:(.text+0x6a8): undefined reference to `png_read_info'
/usr/bin/ld: clip_x11.cpp:(.text+0x6ea): undefined reference to `png_get_IHDR'
/usr/bin/ld: clip_x11.cpp:(.text+0x747): undefined reference to `png_get_rowbytes'
/usr/bin/ld: clip_x11.cpp:(.text+0x8bf): undefined reference to `png_set_strip_16'
/usr/bin/ld: clip_x11.cpp:(.text+0x8ce): undefined reference to `png_set_packing'
/usr/bin/ld: clip_x11.cpp:(.text+0x8dd): undefined reference to `png_set_expand_gray_1_2_4_to_8'
/usr/bin/ld: clip_x11.cpp:(.text+0x8ec): undefined reference to `png_set_palette_to_rgb'
/usr/bin/ld: clip_x11.cpp:(.text+0x8fb): undefined reference to `png_set_gray_to_rgb'
/usr/bin/ld: clip_x11.cpp:(.text+0x90a): undefined reference to `png_set_tRNS_to_alpha'
/usr/bin/ld: clip_x11.cpp:(.text+0x919): undefined reference to `png_set_interlace_handling'
/usr/bin/ld: clip_x11.cpp:(.text+0x938): undefined reference to `png_read_update_info'
/usr/bin/ld: clip_x11.cpp:(.text+0x95a): undefined reference to `png_malloc'
/usr/bin/ld: clip_x11.cpp:(.text+0x9ab): undefined reference to `png_malloc'
/usr/bin/ld: clip_x11.cpp:(.text+0xa19): undefined reference to `png_read_rows'
/usr/bin/ld: clip_x11.cpp:(.text+0xbe0): undefined reference to `png_free'
/usr/bin/ld: clip_x11.cpp:(.text+0xc05): undefined reference to `png_free'
/usr/bin/ld: clip_x11.cpp:(.text+0xc4b): undefined reference to `png_destroy_read_struct'
collect2: error: ld returned 1 exit status
It is still not clear to me what the problem here is.