Fix gcc build exclude on travis

[teor2345]

The main build doesn't use HARDENING_OPTIONS, so the exclude shouldn't,
either. Reduces the number of builders by one.

[coveralls]

Pull Request Test Coverage Report for Build 5895

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.003%) to 60.267%

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Files with Coverage Reduction	New Missed Lines	%
src/feature/hs/hs_common.c	1	83.28%
src/feature/hs/hs_service.c	1	73.72%

Totals
Change from base Build 5834:	-0.003%
Covered Lines:	42855
Relevant Lines:	71108

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💛 - Coveralls