../src/cpu_info.c:37:20: error: use of undeclared identifier '_SC_NPROCESSORS_ONLN'
    return sysconf(_SC_NPROCESSORS_ONLN);
                   ^

--- meson.build.orig	2020-06-30 19:00:42 UTC
+++ meson.build
@@ -26,9 +26,6 @@ if host_machine.system() == 'linux'
 elif host_machine.system() == 'darwin'
     test_args += '-D_DARWIN_C_SOURCE'
     add_project_arguments('-D_DARWIN_C_SOURCE', language: 'c')
-else
-    test_args += '-D_POSIX_C_SOURCE=200112L'
-    add_project_arguments('-D_POSIX_C_SOURCE=200112L', language: 'c')
 endif
 
 # Header checks