Add initial support for Cosmopolitan Libc

Author: petk

cmake/cmake/modules/PHP/StandardLibrary.cmake

@@ -9,6 +9,7 @@ Determine the C standard library used for the build.
 
   Lowercase name of the C standard library:
 
+    * `cosmopolitan`
     * `dietlibc`
     * `glibc`
     * `llvm`
@@ -65,6 +66,17 @@ if(_PHP_C_STANDARD_LIBRARY_DIETLIBC)
   return()
 endif()
 
+# The Cosmopolitan Libc.
+cmake_push_check_state(RESET)
+  set(CMAKE_REQUIRED_QUIET TRUE)
+  check_symbol_exists(__COSMOPOLITAN__ "" _PHP_C_STANDARD_LIBRARY_COSMOPOLITAN)
+cmake_pop_check_state()
+if(_PHP_C_STANDARD_LIBRARY_COSMOPOLITAN)
+  set_property(CACHE PHP_C_STANDARD_LIBRARY PROPERTY VALUE "cosmopolitan")
+  message(CHECK_PASS "Cosmopolitan Libc")
+  return()
+endif()
+
 # The GNU C standard library has __GLIBC__ and __GLIBC_MINOR__ symbols since the
 # very early version 2.0.
 cmake_push_check_state(RESET)

cmake/cmake/modules/PHP/SystemExtensions.cmake

@@ -118,6 +118,7 @@ target_compile_definitions(
   PHP::SystemExtensions
   INTERFACE
     _ALL_SOURCE=1
+    _COSMO_SOURCE
     _DARWIN_C_SOURCE=1
     _GNU_SOURCE
     _NETBSD_SOURCE=1
@@ -228,6 +229,10 @@ set(PHP_SYSTEM_EXTENSIONS_CODE [[
 #ifndef _ALL_SOURCE
 # define _ALL_SOURCE 1
 #endif
+/* Enable extensions on Cosmopolitan Libc. */
+#ifndef _COSMO_SOURCE
+# define _COSMO_SOURCE
+#endif
 /* Enable general extensions on macOS.  */
 #ifndef _DARWIN_C_SOURCE
 # define _DARWIN_C_SOURCE 1