CMake static lib error "No rule to make target"

I want to use a CMakeLists.txt file to create my library. I want to include other libraries used by my functions, but I receive the following error:

make[2]: *** No rule to make target '/libs/libgsl.a', needed by 'mylib'.  Stop.
make[1]: *** [CMakeFiles/Makefile2:76: CMakeFiles/mylib.dir/all] Error 2
make: *** [Makefile:84: all] Error 2

My CMakeLists.txt looks like the following:

cmake_minimum_required(VERSION 2.8)

project(mylib)

# find header & source
file(GLOB_RECURSE SOURCE_C "src/*.c")
file(GLOB_RECURSE SOURCE_CPP "src/*.cpp")
file(GLOB_RECURSE HEADER "include/*.h")

add_executable(mylib
  ${SOURCE_C}
  ${SOURCE_CPP}
  ${HEADER}
)

# includes
include_directories( /include )
link_directories( /libs )

source_group("Header include" FILES ${HEADER})
source_group("Source src"     FILES ${SOURCE_C})
source_group("Source src"     FILES ${SOURCE_CPP})

# opencv package
find_package( OpenCV REQUIRED)
target_link_libraries(mylib PUBLIC opencv_highgui)

# link libraries
target_link_libraries(${PROJECT_NAME} PUBLIC m)
target_link_libraries(${PROJECT_NAME} PUBLIC /libs/libgsl.a)
target_link_libraries(${PROJECT_NAME} PUBLIC /libs/libz.a)
target_link_libraries(${PROJECT_NAME} PUBLIC /libs/libpng16.a)

My folder structure (of dir mylib looks like the following:

mylib--build
        |
       CMakeLists.txt
        |
       include--my .h files, for static lib headers I have separate folders (e.g. include/gsl/gsl_sort.h)
        |      
       libs--my static libs e.g. libgsl.a
        |
       src--my c and cpp files calling functions from the static libs

I include e.g. the gsl-library to my .cpp file like this:

#include "../include/gsl/gsl_sort.h"

>Solution :

target_link_libraries(${PROJECT_NAME} PUBLIC /libs/libgsl.a)
target_link_libraries(${PROJECT_NAME} PUBLIC /libs/libz.a)
target_link_libraries(${PROJECT_NAME} PUBLIC /libs/libpng16.a)

Should be:

target_link_libraries(${PROJECT_NAME} PUBLIC ${CMAKE_CURRENT_LIST_DIR}/libs/libgsl.a)
target_link_libraries(${PROJECT_NAME} PUBLIC ${CMAKE_CURRENT_LIST_DIR}/libs/libz.a)
target_link_libraries(${PROJECT_NAME} PUBLIC ${CMAKE_CURRENT_LIST_DIR}/libs/libpng16.a)

The way you have it, the libraries should exist in the folder /libs/ instead of a sub-directory of your current directory.