[FIX]: utf8proc include path for system library builds

[x15sr71]

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Problem

CCExtractor uses a non-standard include path for utf8proc in src/lib_ccx/params.c:

• #include <utf8proc/utf8proc.h>

However, utf8proc is installed as <utf8proc.h> (without a subdirectory) on all major platforms:

• Debian/Ubuntu: /usr/include/utf8proc.h
• Fedora/RHEL: /usr/include/utf8proc.h
• Homebrew: $(brew --prefix)/include/utf8proc.h
• Nix: $out/include/utf8proc.h
• vcpkg: installed/<triplet>/include/utf8proc.h

This caused build failures when using the -system-libs flag on Homebrew Linux.

Solution

This PR uses __has_include() to support both paths:

• System builds: Uses <utf8proc.h> (standard location)
• Vendored builds: Uses <utf8proc/utf8proc.h> (CCExtractor's vendored copy)

Also removes the temporary symlink workaround from linux/build as it's no longer needed.

Testing

• Builds with -system-libs and without on Linux
• Docker builds work (vendored)
• macOS builds pass
• windows build pass

[ccextractor-bot]

CCExtractor CI platform finished running the test files on linux. Below is a summary of the test results, when compared to test for commit 63dde6f...:

Report Name	Tests Passed
Broken	13/13
CEA-708	14/14
DVB	7/7
DVD	3/3
DVR-MS	2/2
General	27/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	86/86
Teletext	21/21
WTV	13/13
XDS	34/34

All tests passed completely.

Check the result page for more info.

[ccextractor-bot]

CCExtractor CI platform finished running the test files on windows. Below is a summary of the test results, when compared to test for commit 63dde6f...:

Report Name	Tests Passed
Broken	13/13
CEA-708	14/14
DVB	6/7
DVD	3/3
DVR-MS	2/2
General	25/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	80/86
Teletext	21/21
WTV	13/13
XDS	34/34

NOTE: The following tests have been failing on the master branch as well as the PR:

• ccextractor --autoprogram --out=srt --latin1 --quant 0 85271be4d2..., Last passed:

  Test 7345

• ccextractor --autoprogram --out=ttxt --latin1 --ucla dab1c1bd65..., Last passed:

  Test 7345

• ccextractor --out=srt --latin1 --autoprogram 29e5ffd34b..., Last passed:

  Test 7345

• ccextractor --out=spupng c83f765c66..., Last passed:

  Test 7345

• ccextractor --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7345

• ccextractor --startcreditsnotbefore 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7345

• ccextractor --startcreditsnotafter 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7345

• ccextractor --startcreditsforatleast 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7345

• ccextractor --startcreditsforatmost 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed:

  Test 7345

This PR does not introduce any new test failures. However, some tests are failing on both master and this PR (see above).

Check the result page for more info.