[lldb] Don't use NamedTemporaryFile to test compiler support

You cannot use a NamedTempFile with an external process because it may
not be flushed to disk.  The safest and most portable approach is to
close the file, call the other process and then unlink the file
manually.

Presumably this works fine on Linux, but it fails on Darwin when
targeting remote-linux.

See https://bugs.python.org/issue29573

Author: JDevlieghere

lldb/packages/Python/lldbsuite/test/dotest.py

@@ -45,6 +45,21 @@
 from ..support import seven
 
 
+class OnDiskTempFile:
+    def __init__(self):
+        self.path = None
+
+    def __enter__(self):
+        fd, path = tempfile.mkstemp()
+        os.close(fd)
+        self.path = path
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        if os.path.exists(self.path):
+            os.remove(self.path)
+
+
 def is_exe(fpath):
     """Returns true if fpath is an executable."""
     if fpath is None:
@@ -780,8 +795,8 @@ def canRunLibcxxTests():
         return True, "libc++ always present"
 
     if platform == "linux":
-        with tempfile.NamedTemporaryFile() as f:
-            cmd = [configuration.compiler, "-xc++", "-stdlib=libc++", "-o", f.name, "-"]
+        with OnDiskTempFile() as f:
+            cmd = [configuration.compiler, "-xc++", "-stdlib=libc++", "-o", f.path, "-"]
             p = subprocess.Popen(
                 cmd,
                 stdin=subprocess.PIPE,
@@ -840,8 +855,8 @@ def canRunMsvcStlTests():
     if platform != "windows":
         return False, f"Don't know how to build with MSVC's STL on {platform}"
 
-    with tempfile.NamedTemporaryFile() as f:
-        cmd = [configuration.compiler, "-xc++", "-o", f.name, "-E", "-"]
+    with OnDiskTempFile() as f:
+        cmd = [configuration.compiler, "-xc++", "-o", f.path, "-E", "-"]
         p = subprocess.Popen(
             cmd,
             stdin=subprocess.PIPE,