Also add a way to read environ without triggering eager init.

Add a `__wasilibc_get_environ` function which returns the value of
`environ` but without performing eager init.

Author: sunfishcode

expected/wasm32-wasi/defined-symbols.txt

@@ -313,6 +313,7 @@ __wasilibc_fd_renumber
 __wasilibc_find_abspath
 __wasilibc_find_relpath
 __wasilibc_find_relpath_alloc
+__wasilibc_get_environ
 __wasilibc_initialize_environ
 __wasilibc_link
 __wasilibc_link_newat

libc-bottom-half/headers/public/wasi/libc-environ.h

@@ -24,6 +24,11 @@ void __wasilibc_deinitialize_environ(void);
 /// referenced in the program.
 void __wasilibc_maybe_reinitialize_environ_eagerly(void);
 
+/// Return the value of the `environ` variable. Using `environ` directly
+/// requires eager initialization of the environment variables. Using this
+/// function instead of `environ` allows initialization to happen lazily.
+char **__wasilibc_get_environ(void);
+
 #ifdef __cplusplus
 }
 #endif

libc-bottom-half/sources/__wasilibc_environ.c

@@ -0,0 +1,14 @@
+#include <wasi/libc-environ.h>
+
+extern char **__wasilibc_environ;
+
+// See the comments in libc-environ.h.
+char **__wasilibc_get_environ(void) {
+    // Perform lazy initialization if needed.
+    __wasilibc_ensure_environ();
+
+    // Return `environ`. Use the `__wasilibc_`-prefixed name so that we don't
+    // pull in the `environ` symbol directly, which would lead to eager
+    // initialization being done instead.
+    return __wasilibc_environ;
+}