Force fallback to traditional executable detection.

This is to fix crbug/591436, which is a blocker on using clang for
simple-chrome.

diff --git a/lib/Support/Unix/Path.inc b/lib/Support/Unix/Path.inc
index 91549606709..1b251f3a93e 100644
--- a/llvm/lib/Support/Unix/Path.inc
+++ b/llvm/lib/Support/Unix/Path.inc
@@ -206,7 +206,7 @@ std::string getMainExecutable(const char *argv0, void *MainAddr) {
 #elif defined(__linux__) || defined(__CYGWIN__)
   char exe_path[MAXPATHLEN];
   const char *aPath = "/proc/self/exe";
-  if (sys::fs::exists(aPath)) {
+  if (false && sys::fs::exists(aPath)) {
     // /proc is not always mounted under Linux (chroot for example).
     ssize_t len = readlink(aPath, exe_path, sizeof(exe_path));
     if (len < 0)