For cases where git isn't on the path, git is an older version that
doesn't support all the flags we need or the repository we are building
is not actually a git repository.

- Sending telemetry isn't really interesting for the CI build.
- Restoring a local package cache also isn't useful.

In the general case, finding the correct crossgen to invoke is non
trivial since there's no strong corespondence between the host Runtime
ID (which is easy to compute) and the RID that crossgen would be
packaged in.

For example both RHEL and Centos have crossgen packaged in a nuget
packages that uses `rhel.7-x64` as the RID, in order to share the
package across minor versions of RHEL and Centos (which is binary
compatibile).

Since we can build Roslyn without crossgening the bootstrapped
toolchain, I'm exposing an option to allow skipping of crossgen for
platforms where a developer knows apriori that `crossgen.sh` would not
compute the correct RID and fail.

The --release flag was being ignored to cibuild.sh because the define we
pass to Make was set before we actually checked the command line arguments
to cibuild.sh.  There was also a casing typo in a variable name the script
was using which caused the BUILD_CONFIGURATION setting to never be passed
when building the non bootstrap projects.

This was used to deal with unpredictable crashes of MSBuild.  Now that we're running under CoreCLR want to surface these errors and give feedback to the appropriate team.

By passing --pretty=raw we get the full SHA1s of all parent commits,
as well as the tree SHA1 so we can confirm content as well.

In #8701, a comparison was added for `bsd`. It worked on NetBSD as bash
returns `netbsd` for `echo $OSTYPE`. However, today I discovered that
on FreeBSD, it returns `FreeBSD` with upper cased `BSD`. This change
adds the mixed casing to avoid such problems in future for other
BSD-like OSes.

Add FreeBSD support to build file so that it picks the right path to the GNU make binary (GNU make, which is called ``gmake'' on FreeBSD in order to avoid confusion with BSD Make). The commit also fixes script references to bash with ``env'' in order to make it cross platform (e.g. bash sits in /usr/local/bin/bash not /bin/bash on FreeBSD).

The makefile wasn’t flowing the custom mono path through to the tools
we run during the build.

The LTTNG library version used in CoreCLR requires LTTNG_HOME be set
else it issues a warning on process startup.  This was cluttering up our
linux build output.  Fixing this by exporting the value.

The first phase of Linux / Mac builds is to build the csc / vbc executables used to build the repo.  That initial sttep must use csc / vbc to build our compilers.  Previously this was just using our NuGet distributed compilers under Mono.  Now it uses our compilers running on coreclr.

Ideally this would be the same compilers as our NuGet packages.  That's not quite available today.  Hence this is built off a spefici SHA instead.

This changes the Mac builds to use coreclr for running csc and vbc

This changes the compilers and server to exit the process when a Debug.Assert
call fails in a bootstrap build.  The current behavior of throwing up a dialog
blocks the Jenkins build until a timeout occurs and leaves no data.  Now a full
stack trace will be printed, the process exits with a non-zero exit code and the
entire run will fail promptly.

This includes the CPS SDK so that C#/VB CPS implementation can be merged into future.