[debuginfo-tests][dexter] add requires lldb to two tests

both deferred_globals.cpp namespace.cpp require lldb in order to run and will
fail if it's not available.

add the required lines to the top of the tests.

debuginfo-tests/dexter-tests/deferred_globals.cpp

@@ -2,6 +2,7 @@
 // Ensure that debug information for a local variable does not hide
 // a global definition that has the same name.
 
+// REQUIRES: lldb
 // UNSUPPORTED: system-windows
 
 // RUN: %dexter --fail-lt 1.0 -w \

debuginfo-tests/dexter-tests/namespace.cpp

@@ -2,6 +2,7 @@
 // Ensure that the debug information for a global variable includes
 // namespace information.
 
+// REQUIRES: lldb
 // UNSUPPORTED: system-windows
 
 // RUN: %dexter --fail-lt 1.0 -w \