Cherry-pick some cmake commits (#24720)

* Build system: Support  new in cmake 3.17 Ninja Multi-Config generator

(cherry picked from commit 369b618d4f160816818681ed7e41063e2d9ba5b5)

* Build system: Fixed PCH with MSVC & Ninja generator

(cherry picked from commit d669f46b6d5190dabc686a35656e8b03f5ec325b)

* Core: Fix clang 10 warnings

(cherry picked from commit 7272508cb4b51ec5591b6f0e542ea29091db7546)

* Build system: Set -Wno-deprecated-copy only for clang 10

(cherry picked from commit 7fdeb259ba398d5d9343a5dcd1a89562dfcbe981)

* Core/Misc: GCC build and warning fixes

(cherry picked from commit 4d69cc1c567180b408ddbadb9edf26859cf4c006)

* Build system: Print found git version when warning about it being too old

(cherry picked from commit 1ae72db201189877c1b863fac140eb4b0a45c5bb)

* Build system: Removed hard requirement on BOOST_ROOT being set as environment variable, it can now be also passed as command line argument to cmake and fix compile warning with boost 1.73

(cherry picked from commit 161944b7643c62f9e7705c64e42d42e5d07f1959)

* Remove some code that was already removed from 335 and then cherry-picked into master

Co-authored-by: Shauren <shauren.trinity@gmail.com>
(cherry picked from commit 8c09b6e58b0e4f33b7a8e376a28709e693cf2914)

src/server/game/Entities/GameObject/GameObject.cpp

@@ -439,7 +439,6 @@ void GameObject::Update(uint32 diff)
                     m_lootState = GO_READY;                         // for other GOis same switched without delay to GO_READY
                     break;
             }
-            // NO BREAK for switch (m_lootState)
         }
         /* fallthrough */
         case GO_READY: