About pthread: in the simplest project : cmake good:

 (20200923: work)
Determining if the pthread_create exist failed with the following output:
...
CheckSymbolExists.c:(.text+0x4): undefined reference to `pthread_create'
...

Check if HAVE_PTHREAD_CREATE exists or not.

------ check starts. ---------
grep -R . | grep HAVE_PTHREAD_CREATE
001-HAVE-002.txt:001-HAVE-001.txt:build/CMakeCache.txt:CMAKE_HAVE_PTHREAD_CREATE:INTERNAL=1
001-HAVE-002.txt:build/CMakeCache.txt:CMAKE_HAVE_PTHREAD_CREATE:INTERNAL=1
001-HAVE-001.txt:build/CMakeCache.txt:CMAKE_HAVE_PTHREAD_CREATE:INTERNAL=1
build/CMakeCache.txt:CMAKE_HAVE_PTHREAD_CREATE:INTERNAL=1
------ check ends. ---------

We can understand CMAKE_BINARY_DIR is already set assumed, which is automation-parameters.

CMakeLists.txt:set(wxBINARY_DIR ${CMAKE_BINARY_DIR})

1. Create in "main.h" #define PTHREAD  1

2. Write the below in CMakeLists.txt
set(wxSOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
set(wxBINARY_DIR ${CMAKE_BINARY_DIR})
set(wxOUTPUT_DIR ${wxBINARY_DIR}/lib)

3. Compilation as "cmake .." inside build folder.

4. Other things:
Ensured inclusion of tiff_directory: their work, we respect.

(20200923: wxWidgets)
---
$ grep -R . |grep wxSOURCE_DIR | grep zlib
build/cmake/lib/zlib.cmake:    set(ZLIB_INCLUDE_DIRS ${wxSOURCE_DIR}/src/zlib)
---
$ grep -R . |grep wxSOURCE_DIR | grep tiff
build/cmake/lib/tiff.cmake:        ${wxSOURCE_DIR}/src/tiff/libtiff
build/cmake/lib/tiff.cmake:    set(TIFF_INCLUDE_DIRS ${wxSOURCE_DIR}/src/tiff/libtiff)
---
$ grep -R . |grep wxSOURCE_DIR | grep TIFF_INCLUDE_DIRS
build/cmake/lib/tiff.cmake:    set(TIFF_INCLUDE_DIRS ${wxSOURCE_DIR}/src/tiff/libtiff)
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Always, they helps us.

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Beautiful their work especially window customized: How to CMake Good - 2e - Source/Binary Directories and add_subdirectory() 

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