cmake: sync GSS config code with other deps

[vszakats]

• stop passing explicit libpaths via CMAKE_SHARED_LINKER_FLAGS and
  CMAKE_EXE_LINKER_FLAGS. link_directories() is doing that already.
• use curl_required_libpaths() to pass libpaths to the feature test.
  Reported-by: Daniel Engberg
  Fixes cmake: don't use quotes for GSS-API paths #15536
  Also fixes GSS feature detection with non-gcc/clang compilers,
  such as MSVC.
• add libpaths to CURL_LIBPATHS.
• move GSS_CFLAGS, GSS_LDFLAGS stringifications to FindGSS.
  To match the CFLAGS format returned by the rest of Find modules.
• reorder calls to match other dependencies.
• don't extend system LDFLAGS when FindGSS did not return any.
• ignore LDFLAGS when detecting GSS via pkg-config. LDFLAGS holds
  a copy of libpaths and libs in this case. Ignore those to avoid these
  duplicates making into libcurl.pc and curl-config. Also syncing
  behavior with other Find modules which also ignore raw LDFLAGS.
• ignore raw LDFLAGS coming from krb5-config --libs. FindGSS
  no longer returns dependency-specific LDFLAGS after this. Syncing
  behavior with other Find modules.
• reduce scope of checker state push/pop/set.

---

w/o whitespace: https://github.com/curl/curl/pull/15545/files?w=1

[dfandrich]

Analysis of PR #15545 at 97a8fcd5:

Test 310 failed, which has NOT been flaky recently, so there could be a real issue in this PR.

Generated by Testclutch

[diizzyy]

Using GSS in base, path is now missing is pc file

-- FindGSS krb5-config --cflags: -I/usr/include
-- FindGSS krb5-config --libs: -L/usr/lib -lgssapi -lgssapi_krb5 -lheimntlm -lkrb5 -lhx509 -lcom_err -lcrypto -lasn1 -lwind -lheimbase -lroken -lcrypt -pthread
-- Found GSS: Heimdal (found version "FreeBSD heimdal 1.1.0")

[vszakats]

Using GSS in base, path is now missing is pc file

-- FindGSS krb5-config --cflags: -I/usr/include
-- FindGSS krb5-config --libs: -L/usr/lib -lgssapi -lgssapi_krb5 -lheimntlm -lkrb5 -lhx509 -lcom_err -lcrypto -lasn1 -lwind -lheimbase -lroken -lcrypt -pthread
-- Found GSS: Heimdal (found version "FreeBSD heimdal 1.1.0")

curl's CMake do not add system libpaths to the .pc file. As detected via CMAKE_SYSTEM_PREFIX_PATH with some extra logic applied.

Before this patch this logic was accidentally circumvented for libpaths detected in this single GSS detection codepath, that's why it was there before.

Is this causing any fallouts in your case?

[diizzyy]

Works for me (tm) but it's inconsistent with GNU Autotools?

[vszakats]

Works for me (tm) but it's inconsistent with GNU Autotools?

Thanks for your tests!

Yes, it seems inconsistent indeed.

Assuming the CMake way is accurate, it would be nice in autotools too, though so far no one complained. Figuring out the system paths in autotools is also kind of difficult and manual. Something for a future PR.