Bump minimum MSVC version by one dot release to VS 2019 16.8

[chandlerc]

This is a small change, but unblocks using longer string literals in LLVM's source code, and hopefully isn't disruptive.

Discussed in an RFC here: https://discourse.llvm.org/t/rfc-raising-minimum-msvc-version-by-one-dot-release/

[aganea]

Could you also please add an entry in the release notes?

[chandlerc]

Could you also please add an entry in the release notes?

Good suggestion, done hopefully.

[zmodem]

lgtm

[llvm-ci]

LLVM Buildbot has detected a new failure on builder clang-aarch64-sve-vls running on linaro-g3-04 while building llvm at step 7 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/143/builds/3940

Here is the relevant piece of the build log for the reference

Step 7 (ninja check 1) failure: stage 1 checked (failure)
******************** TEST 'AddressSanitizer-aarch64-linux-dynamic :: TestCases/Posix/halt_on_error-signals.c' FAILED ********************
Exit Code: 1

Command Output (stderr):
--
RUN: at line 3: /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/stage1/./bin/clang  -fsanitize=address -mno-omit-leaf-frame-pointer -fno-omit-frame-pointer -fno-optimize-sibling-calls -gline-tables-only   -Wthread-safety -Wthread-safety-reference -Wthread-safety-beta   -shared-libasan -fsanitize-recover=address -pthread /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/llvm/compiler-rt/test/asan/TestCases/Posix/halt_on_error-signals.c -o /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/stage1/runtimes/runtimes-bins/compiler-rt/test/asan/AARCH64LinuxDynamicConfig/TestCases/Posix/Output/halt_on_error-signals.c.tmp
+ /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/stage1/./bin/clang -fsanitize=address -mno-omit-leaf-frame-pointer -fno-omit-frame-pointer -fno-optimize-sibling-calls -gline-tables-only -Wthread-safety -Wthread-safety-reference -Wthread-safety-beta -shared-libasan -fsanitize-recover=address -pthread /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/llvm/compiler-rt/test/asan/TestCases/Posix/halt_on_error-signals.c -o /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/stage1/runtimes/runtimes-bins/compiler-rt/test/asan/AARCH64LinuxDynamicConfig/TestCases/Posix/Output/halt_on_error-signals.c.tmp
In file included from /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/llvm/compiler-rt/test/asan/TestCases/Posix/halt_on_error-signals.c:11:
In file included from /usr/include/stdio.h:27:
In file included from /usr/include/aarch64-linux-gnu/bits/libc-header-start.h:33:
/usr/include/features.h:194:3: warning: "_BSD_SOURCE and _SVID_SOURCE are deprecated, use _DEFAULT_SOURCE" [-W#warnings]
  194 | # warning "_BSD_SOURCE and _SVID_SOURCE are deprecated, use _DEFAULT_SOURCE"
      |   ^
1 warning generated.
RUN: at line 5: env ASAN_OPTIONS=halt_on_error=false:suppress_equal_pcs=false  /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/stage1/runtimes/runtimes-bins/compiler-rt/test/asan/AARCH64LinuxDynamicConfig/TestCases/Posix/Output/halt_on_error-signals.c.tmp 100 >/home/tcwg-buildbot/worker/clang-aarch64-sve-vls/stage1/runtimes/runtimes-bins/compiler-rt/test/asan/AARCH64LinuxDynamicConfig/TestCases/Posix/Output/halt_on_error-signals.c.tmp.log 2>&1 || true
+ env ASAN_OPTIONS=halt_on_error=false:suppress_equal_pcs=false /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/stage1/runtimes/runtimes-bins/compiler-rt/test/asan/AARCH64LinuxDynamicConfig/TestCases/Posix/Output/halt_on_error-signals.c.tmp 100
+ true
RUN: at line 7: FileCheck --check-prefix=CHECK-COLLISION /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/llvm/compiler-rt/test/asan/TestCases/Posix/halt_on_error-signals.c </home/tcwg-buildbot/worker/clang-aarch64-sve-vls/stage1/runtimes/runtimes-bins/compiler-rt/test/asan/AARCH64LinuxDynamicConfig/TestCases/Posix/Output/halt_on_error-signals.c.tmp.log || FileCheck --check-prefix=CHECK-NO-COLLISION /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/llvm/compiler-rt/test/asan/TestCases/Posix/halt_on_error-signals.c </home/tcwg-buildbot/worker/clang-aarch64-sve-vls/stage1/runtimes/runtimes-bins/compiler-rt/test/asan/AARCH64LinuxDynamicConfig/TestCases/Posix/Output/halt_on_error-signals.c.tmp.log
+ FileCheck --check-prefix=CHECK-COLLISION /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/llvm/compiler-rt/test/asan/TestCases/Posix/halt_on_error-signals.c
/home/tcwg-buildbot/worker/clang-aarch64-sve-vls/llvm/compiler-rt/test/asan/TestCases/Posix/halt_on_error-signals.c:29:22: error: CHECK-COLLISION: expected string not found in input
 // CHECK-COLLISION: AddressSanitizer: nested bug in the same thread, aborting
                     ^
<stdin>:1:1: note: scanning from here
=================================================================
^
<stdin>:13:10: note: possible intended match here
SUMMARY: AddressSanitizer: use-after-poison /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/llvm/compiler-rt/test/asan/TestCases/Posix/halt_on_error-signals.c:32:12 in error
         ^

Input file: <stdin>
Check file: /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/llvm/compiler-rt/test/asan/TestCases/Posix/halt_on_error-signals.c

-dump-input=help explains the following input dump.

Input was:
<<<<<<
            1: ================================================================= 
check:29'0     X~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ error: no match found
            2: ==1275191==ERROR: AddressSanitizer: use-after-poison on address 0xaaaabe764160 at pc 0xaaaabe751c24 bp 0xfbff7befe620 sp 0xfbff7befe618 
check:29'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            3: WRITE of size 1 at 0xaaaabe764160 thread T1 
check:29'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            4:  #0 0xaaaabe751c20 in error /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/llvm/compiler-rt/test/asan/TestCases/Posix/halt_on_error-signals.c:32:12 
check:29'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            5:  #1 0xaaaabe751fd0 in receiver /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/llvm/compiler-rt/test/asan/TestCases/Posix/halt_on_error-signals.c:66:5 
check:29'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            6:  #2 0xffff7f824208 in asan_thread_start(void*) /home/tcwg-buildbot/worker/clang-aarch64-sve-vls/llvm/compiler-rt/lib/asan/asan_interceptors.cpp:239:28 
check:29'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            7:  #3 0xffff7f59d5c4 in start_thread nptl/pthread_create.c:442:8 
check:29'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...