qt6: prevent finding zstd when it is disabled

[jcar87]

Summary

Changes to recipe: qt/6

Motivation

Fix #24639

Details

the qt build system searches for zstd even when it is not required - the zstd find logic searches for "thread". If zstd is present (outside of conan), it will find it, which causes to search for Thread::Thread as a transitive dependency, and when it comes to promoting the target to global, it will fail.
This prevents cmake from locating zstd when it is not explicitly required by the recipe.

---

• Read the contributing guidelines
• Checked that this PR is not a duplicate: list of PRs by recipe
• Tested locally with at least one configuration using a recent version of Conan

[conan-center-bot]

Conan v1 pipeline ✔️

All green in build 2 (415b3acfe776bb2eb6a996743c7e759023d808d9):

• qt/6.7.1:
  All packages built successfully! (All logs)

• qt/6.7.0:
  All packages built successfully! (All logs)

• qt/6.6.0:
  All packages built successfully! (All logs)

• qt/6.6.1:
  All packages built successfully! (All logs)

• qt/6.6.3:
  All packages built successfully! (All logs)

• qt/6.6.2:
  All packages built successfully! (All logs)

• qt/6.3.2:
  All packages built successfully! (All logs)

• qt/6.5.3:
  All packages built successfully! (All logs)

• qt/6.4.2:
  All packages built successfully! (All logs)

---

Conan v2 pipeline ✔️

Note: Conan v2 builds are now mandatory. Please read our discussion about it.

All green in build 1 (415b3acfe776bb2eb6a996743c7e759023d808d9):

• qt/6.7.1:
  All packages built successfully! (All logs)

• qt/6.7.0:
  All packages built successfully! (All logs)

• qt/6.6.3:
  All packages built successfully! (All logs)

• qt/6.3.2:
  All packages built successfully! (All logs)

• qt/6.6.2:
  All packages built successfully! (All logs)

• qt/6.4.2:
  All packages built successfully! (All logs)

• qt/6.6.0:
  All packages built successfully! (All logs)

• qt/6.5.3:
  All packages built successfully! (All logs)

• qt/6.6.1:
  All packages built successfully! (All logs)

[github-actions]

Hooks produced the following warnings for commit 415b3ac

qt/6.7.1@#36c25b343703345eefaccd43bac02b19

post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library '.\plugins\tls\qschannelbackend.dll' links to system library 'ncrypt' but it is not in cpp_info.system_libs.
post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library '.\plugins\tls\qschannelbackendd.dll' links to system library 'ncrypt' but it is not in cpp_info.system_libs.

qt/6.7.0@#7a0dca522c5cc760ac22e0c066f714ed

post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library '.\plugins\tls\qschannelbackendd.dll' links to system library 'ncrypt' but it is not in cpp_info.system_libs.
post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library '.\plugins\tls\qschannelbackend.dll' links to system library 'ncrypt' but it is not in cpp_info.system_libs.

qt/6.6.0@#c96d97ae00c69e632ba9a4869ed218ad

post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library './plugins/platforms/libqcocoa.dylib' links to system library 'ColorSync' but it is not in cpp_info.frameworks.
post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library './plugins/platforms/libqcocoa_debug.dylib' links to system library 'ColorSync' but it is not in cpp_info.frameworks.
post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library '.\plugins\tls\qschannelbackend.dll' links to system library 'ncrypt' but it is not in cpp_info.system_libs.
post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library '.\plugins\tls\qschannelbackendd.dll' links to system library 'ncrypt' but it is not in cpp_info.system_libs.

qt/6.6.1@#683dac33de111a2f33634e0b9dc2f9d0

post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library '.\plugins\tls\qschannelbackend.dll' links to system library 'ncrypt' but it is not in cpp_info.system_libs.
post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library '.\plugins\tls\qschannelbackendd.dll' links to system library 'ncrypt' but it is not in cpp_info.system_libs.

qt/6.6.3@#b1e098c68a8bcbfefc71700404f13611

post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library '.\plugins\tls\qschannelbackend.dll' links to system library 'ncrypt' but it is not in cpp_info.system_libs.
post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library '.\plugins\tls\qschannelbackendd.dll' links to system library 'ncrypt' but it is not in cpp_info.system_libs.

qt/6.6.2@#3e8cade501d4142bc3309679ed206236

post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library '.\plugins\tls\qschannelbackendd.dll' links to system library 'ncrypt' but it is not in cpp_info.system_libs.
post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library '.\plugins\tls\qschannelbackend.dll' links to system library 'ncrypt' but it is not in cpp_info.system_libs.

qt/6.3.2@#64339adb17c17e3077ade02cc4c7ab4f

post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library './plugins/platforms/libqcocoa_debug.dylib' links to system library 'ColorSync' but it is not in cpp_info.frameworks.
post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library './plugins/platforms/libqcocoa.dylib' links to system library 'ColorSync' but it is not in cpp_info.frameworks.

qt/6.5.3@#e06a51aa5592c851ec28597a13fcbfd5

post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library './plugins/platforms/libqcocoa.dylib' links to system library 'ColorSync' but it is not in cpp_info.frameworks.
post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library './plugins/platforms/libqcocoa_debug.dylib' links to system library 'ColorSync' but it is not in cpp_info.frameworks.

qt/6.4.2@#2888a1f1f959da406744dd06920abed3

post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library './plugins/platforms/libqcocoa.dylib' links to system library 'ColorSync' but it is not in cpp_info.frameworks.
post_package(): WARN: [MISSING SYSTEM LIBS (KB-H043)] Library './plugins/platforms/libqcocoa_debug.dylib' links to system library 'ColorSync' but it is not in cpp_info.frameworks.