Set environment variable "PREFIX", it will be used by invoked shell
script, e.g. the shell script uses it to find lib paths.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
---
 tools/lib/subcmd/exec-cmd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/lib/subcmd/exec-cmd.c b/tools/lib/subcmd/exec-cmd.c
index 33e94fb83986..5dbea456973e 100644
--- a/tools/lib/subcmd/exec-cmd.c
+++ b/tools/lib/subcmd/exec-cmd.c
@@ -24,6 +24,9 @@ void exec_cmd_init(const char *exec_name, const char *prefix,
 	subcmd_config.prefix		= prefix;
 	subcmd_config.exec_path		= exec_path;
 	subcmd_config.exec_path_env	= exec_path_env;
+
+	/* Setup environment variable for invoked shell script. */
+	setenv("PREFIX", prefix, 1);
 }
 
 #define is_dir_sep(c) ((c) == '/')
-- 
2.25.1