Skip test_fork on macOS (#4616)

Author: chikle9090

docs/source/install.rst

@@ -149,9 +149,10 @@ Build requirements
 - C++17 compiler
 - CMake >= 3.16
 - SQLite3 >= 3.11: headers and library for target architecture, and sqlite3 executable for build architecture
-- libtiff >= 4.0 (optional but recommended to read grid formats based on GeoTIFF. Only basic TIFF support is required; optional features like WebP or ZStd are not needed.)
-- curl >= 7.29.0 (optional but recommended to download required grids at runtime.)
-- JSON for Modern C++ (nlohmann/json) >= 3.7.0; if not found as an external dependency then vendored version 3.9.1 from PROJ source tree is used
+- libtiff >= 4.0 (optional but recommended to enable reading of grid formats based on GeoTIFF. Only basic TIFF support is required; optional features like WebP or ZStd are not needed.)
+- curl >= 7.29.0 (optional but recommended to support automatic downloading of remote grid files during runtime, allowing PROJ to fetch required transformation data on demand.)
+- JSON for Modern C++ (nlohmann/json) >= 3.7.0
+
 
 .. _test_requirements:
 

test/unit/CMakeLists.txt

@@ -255,7 +255,7 @@ add_test(NAME test_misc COMMAND test_misc)
 set_property(TEST test_misc
   PROPERTY ENVIRONMENT ${PROJ_TEST_ENVIRONMENT})
 
-if (Threads_FOUND AND CMAKE_USE_PTHREADS_INIT)
+if (Threads_FOUND AND CMAKE_USE_PTHREADS_INIT AND NOT APPLE)
 add_definitions(-DPROJ_HAS_PTHREADS)
 add_executable(test_fork
   test_fork.c)