Introduce helper functions for safe fork+exec of processes

In some situations, we want to execute an external shell command
in a non-blocking way.  Similar to 'system', but without waiting for
the child to complete.  We also want to close all file descriptors
ahead of the exec() and filter + modify the environment.

Change-Id: Ib24ac8a083db32e55402ce496a5eabd8749cc888
Related: OS#4332
diff --git a/configure.ac b/configure.ac
index e45ec9f..1056a0a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -282,7 +282,7 @@
 	)],
 	[embedded=$enableval], [embedded="no"])
 
-AM_CONDITIONAL(ENABLE_STATS_TEST, true)
+AM_CONDITIONAL(EMBEDDED, false)
 AM_CONDITIONAL(ENABLE_SERCOM_STUB, false)
 
 if test x"$embedded" = x"yes"
@@ -301,7 +301,7 @@
 	AM_CONDITIONAL(ENABLE_PCSC, false)
 	AM_CONDITIONAL(ENABLE_PSEUDOTALLOC, true)
 	AM_CONDITIONAL(ENABLE_SERCOM_STUB, true)
-	AM_CONDITIONAL(ENABLE_STATS_TEST, false)
+	AM_CONDITIONAL(EMBEDDED, true)
 	AC_DEFINE([USE_GNUTLS], [0])
 	AC_DEFINE([PANIC_INFLOOP],[1],[Use infinite loop on panic rather than fprintf/abort])
 fi