Fix build errors on some configurations

It's been reported
<http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20180611/559616.html>
that template argument deduction for RetryAfterSignal fails if open is
not prefixed with "::".

This should help us build correctly on those platforms and explicitly
specifying the namespace is more correct anyway.

llvm-svn: 334403
diff --git a/llvm/lib/Support/Unix/Path.inc b/llvm/lib/Support/Unix/Path.inc
index 9800f86..b4001fb 100644
--- a/llvm/lib/Support/Unix/Path.inc
+++ b/llvm/lib/Support/Unix/Path.inc
@@ -767,7 +767,7 @@
 
   SmallString<128> Storage;
   StringRef P = Name.toNullTerminatedStringRef(Storage);
-  if ((ResultFD = sys::RetryAfterSignal(-1, open, P.begin(), OpenFlags, Mode)) <
+  if ((ResultFD = sys::RetryAfterSignal(-1, ::open, P.begin(), OpenFlags, Mode)) <
       0)
     return std::error_code(errno, std::generic_category());
 #ifndef O_CLOEXEC
diff --git a/llvm/lib/Support/Unix/Process.inc b/llvm/lib/Support/Unix/Process.inc
index 43ba6d6..fa515d4 100644
--- a/llvm/lib/Support/Unix/Process.inc
+++ b/llvm/lib/Support/Unix/Process.inc
@@ -199,7 +199,7 @@
   for (int StandardFD : StandardFDs) {
     struct stat st;
     errno = 0;
-    if (RetryAfterSignal(-1, fstat, StandardFD, &st) < 0) {
+    if (RetryAfterSignal(-1, ::fstat, StandardFD, &st) < 0) {
       assert(errno && "expected errno to be set if fstat failed!");
       // fstat should return EBADF if the file descriptor is closed.
       if (errno != EBADF)
@@ -211,7 +211,7 @@
     assert(errno == EBADF && "expected errno to have EBADF at this point!");
 
     if (NullFD < 0) {
-      if ((NullFD = RetryAfterSignal(-1, open, "/dev/null", O_RDWR)) < 0)
+      if ((NullFD = RetryAfterSignal(-1, ::open, "/dev/null", O_RDWR)) < 0)
         return std::error_code(errno, std::generic_category());
     }