Workaround Clang 18 issues in our test suite (#4932)

tests/libcxx/expected_results.txt

@@ -1291,6 +1291,17 @@ std/ranges/range.utility/range.utility.conv/to.pass.cpp:9 SKIPPED
 std/thread/thread.jthread/assign.move.pass.cpp:9 SKIPPED
 std/utilities/meta/meta.unary/dependent_return_type.compile.pass.cpp:9 SKIPPED
 
+# These tests also need ADDITIONAL_COMPILE_FLAGS to silence warnings, but only for Clang 18.
+# TRANSITION, Clang 19
+std/containers/associative/map/map.modifiers/insert_range.pass.cpp:9 SKIPPED
+std/containers/associative/multimap/multimap.modifiers/insert_range.pass.cpp:9 SKIPPED
+std/containers/associative/multiset/insert_range.pass.cpp:9 SKIPPED
+std/containers/associative/set/insert_range.pass.cpp:9 SKIPPED
+std/containers/unord/unord.map/unord.map.modifiers/insert_range.pass.cpp:9 SKIPPED
+std/containers/unord/unord.multimap/unord.multimap.modifiers/insert_range.pass.cpp:9 SKIPPED
+std/containers/unord/unord.multiset/insert_range.pass.cpp:9 SKIPPED
+std/containers/unord/unord.set/insert_range.pass.cpp:9 SKIPPED
+
 # This test is marked as `XFAIL: msvc`, but the MSVC-internal test harness doesn't yet parse XFAIL.
 std/utilities/function.objects/func.wrap/func.wrap.func/noncopyable_return_type.pass.cpp:9 SKIPPED
 

tests/std/tests/VSO_0000000_vector_algorithms_floats/env.lst

@@ -42,12 +42,13 @@ PM_CL="/BE /c /EHsc /MD /std:c++14 /w14640 /Zc:threadSafeInit-"
 PM_CL="/BE /c /EHsc /MDd /std:c++17 /permissive- /w14640 /Zc:threadSafeInit-"
 PM_CL="/BE /c /EHsc /MT /std:c++20 /permissive- /w14640 /Zc:threadSafeInit-"
 PM_CL="/BE /c /EHsc /MTd /std:c++latest /permissive- /w14640 /Zc:threadSafeInit-"
-PM_COMPILER="clang-cl" PM_CL="-fno-ms-compatibility -fno-delayed-template-parsing -Wno-unqualified-std-cast-call /EHsc /MD /std:c++14 /w14640 /Zc:threadSafeInit- --start-no-unused-arguments"
-PM_COMPILER="clang-cl" PM_CL="-fno-ms-compatibility -fno-delayed-template-parsing -Wno-unqualified-std-cast-call /EHsc /MDd /std:c++17 /w14640 /Zc:threadSafeInit- --start-no-unused-arguments"
-PM_COMPILER="clang-cl" PM_CL="-fno-ms-compatibility -fno-delayed-template-parsing -Wno-unqualified-std-cast-call /EHsc /MT /std:c++20 /permissive- /w14640 /Zc:threadSafeInit- --start-no-unused-arguments"
-PM_COMPILER="clang-cl" PM_CL="-fno-ms-compatibility -fno-delayed-template-parsing -Wno-unqualified-std-cast-call /EHsc /MTd /std:c++latest /permissive- /w14640 /Zc:threadSafeInit- --start-no-unused-arguments"
+# TRANSITION, Clang 18: remove `-Wno-unknown-warning-option` from the below five clang-cl configs
+PM_COMPILER="clang-cl" PM_CL="-fno-ms-compatibility -fno-delayed-template-parsing -Wno-unqualified-std-cast-call -Wno-unknown-warning-option -Wno-nan-infinity-disabled /EHsc /MD /std:c++14 /w14640 /Zc:threadSafeInit- --start-no-unused-arguments"
+PM_COMPILER="clang-cl" PM_CL="-fno-ms-compatibility -fno-delayed-template-parsing -Wno-unqualified-std-cast-call -Wno-unknown-warning-option -Wno-nan-infinity-disabled /EHsc /MDd /std:c++17 /w14640 /Zc:threadSafeInit- --start-no-unused-arguments"
+PM_COMPILER="clang-cl" PM_CL="-fno-ms-compatibility -fno-delayed-template-parsing -Wno-unqualified-std-cast-call -Wno-unknown-warning-option -Wno-nan-infinity-disabled /EHsc /MT /std:c++20 /permissive- /w14640 /Zc:threadSafeInit- --start-no-unused-arguments"
+PM_COMPILER="clang-cl" PM_CL="-fno-ms-compatibility -fno-delayed-template-parsing -Wno-unqualified-std-cast-call -Wno-unknown-warning-option -Wno-nan-infinity-disabled /EHsc /MTd /std:c++latest /permissive- /w14640 /Zc:threadSafeInit- --start-no-unused-arguments"
 # TRANSITION, GH-3568
-# PM_COMPILER="clang-cl" PM_CL="-fno-ms-compatibility -fno-delayed-template-parsing -Wno-unqualified-std-cast-call /EHsc /MT /std:c++latest /permissive- /w14640 /Zc:threadSafeInit- -fsanitize=undefined -fno-sanitize-recover=undefined --start-no-unused-arguments"
+# PM_COMPILER="clang-cl" PM_CL="-fno-ms-compatibility -fno-delayed-template-parsing -Wno-unqualified-std-cast-call -Wno-unknown-warning-option -Wno-nan-infinity-disabled /EHsc /MT /std:c++latest /permissive- /w14640 /Zc:threadSafeInit- -fsanitize=undefined -fno-sanitize-recover=undefined --start-no-unused-arguments"
 RUNALL_CROSSLIST
 *	PM_CL="/fp:strict"
 *	PM_CL="/fp:precise"