changed TBB_EXPORT to use gcc visibility attribute

[anton-potapov]

Description

according to GCC symbols visibility wiki page as such (with __attribute__((visibility ("default"))) exported symbols should be explicitly marked, to allow compilating with -fvisibility=hidden flag.

Fixes #779

• [x] - git commit message contains an appropriate signed-off-by string (see CONTRIBUTING.md for details)

Type of change

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• [x] bug fix - change that fixes an issue
• [ ] new feature - change that adds functionality
• [ ] tests - change in tests
• [ ] infrastructure - change in infrastructure and CI
• [ ] documentation - documentation update

Tests

• [ ] added - required for new features and some bug fixes
• [x] not needed

Documentation

• [ ] updated in # - add PR number
• [ ] needs to be updated
• [ ] not needed

Breaks backward compatibility

• [ ] Yes
• [x] No
• [ ] Unknown

Notify the following users

@alexey-katranov

Other information

[phprus]

Also need an export: https://github.com/oneapi-src/oneTBB/blob/09346731f1279feb23c81f569eabe6010c620872/test/tbb/test_dynamic_link.cpp#L31-L39