Fixes https://github.com/mono/mono/issues/10602 .
From the issue:
```
We need to enable this to support the system assemblies conflict
resolution which we now rely on for any new packages to enhance
developers experience and get us out of dependency on specific package
versions.
```
This is part of PR 2430: avoid duplicating degine constants if they exist. This commit splits the condition and definition of the properties in two, because xbuild doesn't support the regex part in a condition. msbuild does, but we need to support both.
The previous change had the fault of considering __UNIFIED__ANYTHING__ the same as __UNIFIED__ and if a user set that property, then he would lose the other (pointed out by jstedfast in the PR).
This commit fixes that.
In VS the property page for Build will show whatever is in DefineConstants, and then save it. Without this, that means that any time the Build page is saved, it duplicates the constants.
This fixes bug#32765: Bug 32765 - Conditional compilation symbols are duplicated everytime I reload the project or restart visual studio (https://bugzilla.xamarin.com/show_bug.cgi?id=32765)
Mono's fork of msbuild uses a `$(_DebugFileExt)` property to specify
the debug file extension (.pdb/.mdb) to use. It defaults to .pdb. So,
with XI/XM, .mdb files don't get copied to the output folder.
We also add a `$(FscDebugFileExt)` property, which allows our default of
`.mdb` to be overridden.
But the `$(_DebugFileExt)` support is not in upstream msbuild yet. So,
we can't ask the F# upstream to add it. Hence, this is being added to
our FSharp target files. Once, all this is upstream, we can remove the
overrides from our files.
Fixes https://bugzilla.xamarin.com/show_bug.cgi?id=51148
Ankit Jain
joj
Jason Imison
Mikayla Hutchinson
Rolf Bjarne Kvinge