perf subcmd: Set environment variable "PREFIX"

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 <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

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) == '/')