Make xabuild smarter in configuration detection

[grendello]

xabuild determines the XA installation prefix by looking at the bin/{Debug,
Release} directories, in the specified order. If one wants to build a project in
the Release configuration and both bin/Debug and bin/Release are present,
xabuild will use bin/Debug as the prefix regardless of the configuration
passed to {ms,x}build with /p:Configuration=Name. Your project will still be
built in the specified configuration but XA assemblies etc will come from the
Debug build of XA - probably not the desired outcome. To work around it you
would need to invoke xabuild as follows:

CONFIGURATION=Release xabuild /p:Configuration=Release my.csproj

which is unnecessarily verbose. This commit makes xabuild slightly smarter by
making it understand the /p:Configuration parameter and extracting the
configuration name from it and setting CONFIGURATION to this value for you.
This is done only if CONFIGURATION is not set when invoking xabuild

[jonpryor]

why is this indenting by two tab stops?

[grendello]

Emacs? :)

[jonpryor]

One problem with this is that people might not use Debug or Release configurations. For example, they could add a new Android-Debug configuration (e.g. if the solution has iOS projects as well, and they don't want to build iOS stuff when doing Android stuff), in which case CONFIGURATION would be set to Android-Debug, which would fail "weirdly" elsewhere.

If we move this logic to be before line 44, when $prefix and $Paths_targets are set, then it should be fine (-ish?), as the [ -d "$prefix/../../bin/$c" ] check on line 50 would prevent use of "invalid" CONFIGURATION values.

[grendello]

I thought about the "invalid" configurations and considered restricting the check on line 166 to just Release and Debug but then I thought that if they pass /p:Configuration=AndroidDebug then no change to the current behavior will be done, since CONFIGURATION will be set to AndroidDebug and since such directory doesn't exist at $prefix, the behavior will be unchanged wrt to the current one (it will simply continue to look for Debug and Release)

[jonpryor]

I still believe that the /p:Configuration parsing needs to occur before line 44.

At present, $CONFIGURATION is only set after $prefix and $Paths_targets has been set. Consequently:

$ xabuild /p:Configuration=Release Project.csproj

would still use a $prefix of bin/Debug, as $prefix is set on line 59, while $CONFIGURATION isn't updated until line 166.

This PR would thus be a no-op, AFAICT.

[jonpryor]

I would prefer it if this were spread across multiple lines:

			/property:Configuration=*|/p:Configuration=*|-p:Configuration=*|--property:Configuration=*)
				CONFIGURATION="`echo $p | cut -d '=' -f 2`"
				;;

This makes it easier for me to read without horizontal scrolling.