env: Allow to set default_environment[] from board code via compile option DEFAULT_ENV_IS_RW

This change allows board code to modify default_environment[] array when
compile option DEFAULT_ENV_IS_RW is specified in board config file.

Some board default variables depend on runtime configuration which is not
known at compile time. Therefore allow to set default_environment[] array
as non-const and allow board code to modify it when it is needed.

Signed-off-by: Pali Rohár <pali@kernel.org>
Acked-by: Andre Heider <a.heider@gmail.com>
diff --git a/include/env_default.h b/include/env_default.h
index 8a0c305..ea31a8e 100644
--- a/include/env_default.h
+++ b/include/env_default.h
@@ -19,6 +19,8 @@
 	{
 #elif defined(DEFAULT_ENV_INSTANCE_STATIC)
 static char default_environment[] = {
+#elif defined(DEFAULT_ENV_IS_RW)
+uchar default_environment[] = {
 #else
 const uchar default_environment[] = {
 #endif
diff --git a/include/env_internal.h b/include/env_internal.h
index b26dc62..708c833 100644
--- a/include/env_internal.h
+++ b/include/env_internal.h
@@ -111,7 +111,11 @@
 extern env_t embedded_environment;
 #endif /* ENV_IS_EMBEDDED */
 
+#ifdef DEFAULT_ENV_IS_RW
+extern unsigned char default_environment[];
+#else
 extern const unsigned char default_environment[];
+#endif
 
 #ifndef DO_DEPS_ONLY