util: Relax conditions on defining _ALLOW_COMPILER_AND_STL_VERSION_MISMATCH.

Author: jeffdav

utils/build.ps1

@@ -1640,11 +1640,11 @@ function Build-Compilers() {
     $PythonRoot = "$BinaryCache\Python$($Arch.CMakeName)-$PythonVersion\tools"
     $PythonLibName = "python{0}{1}" -f ([System.Version]$PythonVersion).Major, ([System.Version]$PythonVersion).Minor
 
-    # The STL in VS 17.10 requires Clang 17 or higher, but Swift toolchains prior to version 6 include older versions
-    # of Clang. If bootstrapping with an older toolchain, we need to relax to relax this requirement with
-    # ALLOW_COMPILER_AND_STL_VERSION_MISMATCH.
+    # The STL in VS 17.10 requires Clang 17 or higher, but released Swift toolchains currently include older versions
+    # of Clang. If bootstrapping with an older toolchain, we need to relax this requirement by defining
+    # _ALLOW_COMPILER_AND_STL_VERSION_MISMATCH. Developer builds are (currently) up-to-date.
     $SwiftFlags = @();
-    if ([System.Version](Get-PinnedToolchainVersion) -lt [System.Version]"6.0" -and [System.Version](Get-PinnedToolchainVersion) -ne [System.Version]"0.0.0") {
+    if ([System.Version](Get-PinnedToolchainVersion) -ne [System.Version]"0.0.0") {
       $SwiftFlags += @("-Xcc", "-D_ALLOW_COMPILER_AND_STL_VERSION_MISMATCH");
     }