Address #1524 - fix meson cross compilation linking.

In the cross compilation case, we need to resolve our
dependencies on libc twice, once for the build machine and once for the
target machine. This includes pthreads, -libc, and android-spawn.

CHANGELOG.md

@@ -2,6 +2,7 @@
 All notable changes to this project will be documented in this file.
 
 ## ??? - Unreleased
+- Fix meson cross compilation
 - Update timeout documentation for networking APIs: timeouts raise errors and do not return nil.
 - Add `janet_addtimeout_nil(double sec);` to the C API.
 - Change string hashing.

meson.build

@@ -26,8 +26,17 @@ project('janet', 'c',
 janet_path = join_paths(get_option('prefix'), get_option('libdir'), 'janet')
 header_path = join_paths(get_option('prefix'), get_option('includedir'), 'janet')
 
-# Link math library on all systems
+# Compilers
 cc = meson.get_compiler('c')
+native_cc = meson.get_compiler('c', native : true)
+
+# Native deps
+native_m_dep = native_cc.find_library('m', required : false)
+native_dl_dep = native_cc.find_library('dl', required : false)
+native_android_spawn_dep = native_cc.find_library('android-spawn', required : false)
+native_thread_dep = dependency('threads', native : true)
+
+# Deps
 m_dep = cc.find_library('m', required : false)
 dl_dep = cc.find_library('dl', required : false)
 android_spawn_dep = cc.find_library('android-spawn', required : false)
@@ -164,11 +173,18 @@ mainclient_src = [
   'src/mainclient/shell.c'
 ]
 
+janet_dependencies = [m_dep, dl_dep, android_spawn_dep]
+janet_native_dependencies = [native_m_dep, native_dl_dep, native_android_spawn_dep]
+if not get_option('single_threaded')
+  janet_dependencies += thread_dep
+  janet_native_dependencies += native_thread_dep
+endif
+
 # Build boot binary
 janet_boot = executable('janet-boot', core_src, boot_src,
   include_directories : incdir,
   c_args : '-DJANET_BOOTSTRAP',
-  dependencies : [m_dep, dl_dep, thread_dep, android_spawn_dep],
+  dependencies : janet_native_dependencies,
   native : true)
 
 # Build janet.c
@@ -181,11 +197,6 @@ janetc = custom_target('janetc',
     'JANET_PATH', janet_path
   ])
 
-janet_dependencies = [m_dep, dl_dep, android_spawn_dep]
-if not get_option('single_threaded')
-  janet_dependencies += thread_dep
-endif
-
 # Allow building with no shared library
 if cc.has_argument('-fvisibility=hidden')
   lib_cflags = ['-fvisibility=hidden']
@@ -231,7 +242,7 @@ if meson.is_cross_build()
   endif
   janet_nativeclient = executable('janet-native', janetc, mainclient_src,
     include_directories : incdir,
-    dependencies : janet_dependencies,
+    dependencies : janet_native_dependencies,
     c_args : extra_native_cflags,
     native : true)
 else