Fix CDT GCC parser to correctly parse C++ commands

Fix CDT GCC parser to correctly parse C++ commands

Previously suggested parser command pattern:

xtensa-esp32-elf-(g?cc)|([gc]\+\+)|(clang)

was incorrect for compilation of c++ files, as it is expanded by Eclipse into or between:

xtensa-esp32-elf-(g?cc)
([gc]\+\+)
(clang)

Additional grouping around existing pattern solves that issue, and helps Eclipse to correctly find ESP-IDF includes.

Merges https://github.com/espressif/esp-idf/pull/1005