kernel & addons: Build with the non-legacy GCC even on x86_gcc2h.

Only one code change: for some reason, GCC chokes on the cr3 functions
as macros (throwing errors about invalid registers.) The BSDs have them
as inline functions instead, so they are converted to that here.

Tested and working. There seems to be about a 10% decrease in CPU time
on some compilation benchmarks that I briefly tried.

Change-Id: I31666297394d7619f83fca6ff5f933ddd6f07420
Reviewed-on: https://review.haiku-os.org/c/haiku/+/4515
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

configure & build: Rework legacy GCC detection to parse versions outside of Jam.

Jam comparison logic is string-based, and so was detecting GCC >= 10
as being < 2. This rectifies that by removing the GCC version parsing
from Jam logic entirely, and setting various BuildConfig variables
instead.

Change-Id: I0c0ae3b9002fb5e77f9ca7a78600c91871657f03
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3293
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>
Reviewed-by: Jérôme Duval <jerome.duval@gmail.com>
Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>

build/jam/BuildFeatureRules: Make EnableBuildFeatures actually work.

It was trying to use $(feature:U) outside of the loop where it is
actually set. Thanks to PulkoMandy for spotting the problem.

(How did this not break tons of stuff?)

rule FFilterByBuildFeatures: Fix output

EnableBuildFeatures: deal with duplicate invocations

build features/bootstrap repo: support secondary arch

* Add rule FSplitPackageName. It splits a package name into port name
and package suffix.
* FSetConditionsHold: Rename to FConditionsHold and replace the set
parameter by a predicate rule parameter, thus adding more flexibility.
* FIsBuildFeatureEnabled: Use the faster check.
* Add rule FQualifiedBuildFeatureName. Given a build feature name, it
prepends the current packaging architecture to yield a qualified
feature name. Is used by the other build feature rules so that the
same build feature can be configured differently for each arch.
* ExtractBuildFeatureArchives: The supplied list is now filtered via
FFilterByBuildFeatures, allowing for build feature conditions in the
list.
* Add rule InitArchitectureBuildFeatures. It is called early for each
configured architecture, setting up some basic build features for it.
"primary" is set for the primary architecture and a "secondary_<arch>"
is set for each secondary architecture.
* BuildFeatures: Add secondary architecture support: Use the correct
paths for libraries and headers (subdir for secondary architecture)
and configure the icu and zlib sources only for the primary
architecture.
* BootstrapPackageRepository: The package lists are now filtered via
FFilterByBuildFeatures, allowing for build feature conditions in the
lists.
* IsPackageAvailable, FetchPackage: Add secondary architecture support.
* HaikuPortsCross/x86_gcc2: Add icu and zlib x86 secondary packages.

The second stage Haiku cross devel package for the secondary
architecture can now be built.

Move build feature rules to separate file

rule FFilterByBuildFeatures: Fix output

EnableBuildFeatures: deal with duplicate invocations

build features/bootstrap repo: support secondary arch

* Add rule FSplitPackageName. It splits a package name into port name
and package suffix.
* FSetConditionsHold: Rename to FConditionsHold and replace the set
parameter by a predicate rule parameter, thus adding more flexibility.
* FIsBuildFeatureEnabled: Use the faster check.
* Add rule FQualifiedBuildFeatureName. Given a build feature name, it
prepends the current packaging architecture to yield a qualified
feature name. Is used by the other build feature rules so that the
same build feature can be configured differently for each arch.
* ExtractBuildFeatureArchives: The supplied list is now filtered via
FFilterByBuildFeatures, allowing for build feature conditions in the
list.
* Add rule InitArchitectureBuildFeatures. It is called early for each
configured architecture, setting up some basic build features for it.
"primary" is set for the primary architecture and a "secondary_<arch>"
is set for each secondary architecture.
* BuildFeatures: Add secondary architecture support: Use the correct
paths for libraries and headers (subdir for secondary architecture)
and configure the icu and zlib sources only for the primary
architecture.
* BootstrapPackageRepository: The package lists are now filtered via
FFilterByBuildFeatures, allowing for build feature conditions in the
lists.
* IsPackageAvailable, FetchPackage: Add secondary architecture support.
* HaikuPortsCross/x86_gcc2: Add icu and zlib x86 secondary packages.

The second stage Haiku cross devel package for the secondary
architecture can now be built.

Move build feature rules to separate file