[build.ps1] Revamp No-asserts toolchain build and packaging

[mhegazy]

This PR allows us to build the noasserts variant of the compilers along with the asserts variant by adding a new commandline argument: -IncludeNoAsserts. This is in preparation for packaging both in our installer and letting users choose which ones to use.

If the new option is not set, the build output should not change from today. if the new option is set compilers are built an extra time with asserts disabled.

Note to reviewers: Reviewing this change one commit at a time should give you a better experience than looking at all changes at once.

Changes:

• Remove existing commandline option -Variant (added in #79313), that was added to allow building one variant at a time.
• Add new command line option -IncludeNoAsserts to build a new version of the compiler with LLVM_ENABLE_ASSERTIONS=NO
• Add an extra call to Build-Compilers when -IncludeNoAsserts is set
• Add an extra step to Build-mimalloc to batch the tools in no-asserts output directory as well
• Fix bug in argument handling in Invoke-BuildStep

[compnerd]

This should likely be split out, this has no impact on the build/packaging only in the internals of the script.

[mhegazy]

@compnerd updated based on your review feedback. mind taking another look

[mhegazy]

@compnerd i realized that PinnedToolchainVariant was causing trouble, speciallyt hat it was not fully supported before. so remvoing it and making it clear where we expect asserts and where we do not should address your comments

[compnerd]

Invoke-Command would be better than &.

[compnerd]

@swift-ci please smoke test

[compnerd]

Error: Positional parameter 'Asserts' found. The Invoke-BuildStep function only supports named parameters after the required Name and Platform parameters.
    at Invoke-BuildStep, C:\Users\swift-ci\jenkins\workspace\swift-PR-windows\swift\utils\build.ps1: line 662
    at <ScriptBlock>, C:\Users\swift-ci\jenkins\workspace\swift-PR-windows\swift\utils\build.ps1: line 3473
  From System.Management.Automation.RuntimeException: Positional parameter 'Asserts' found. The Invoke-BuildStep function only supports named parameters after the required Name and Platform parameters.

[mhegazy]

@compnerd should be running clean now. mind rerunning the smoke test

[compnerd]

@swift-ci please smoke test

[compnerd]

@swift-ci please smoke test