build-presets: Update/simplify incremental Xcode preset

This is our /only/ standard Xcode preset, and it's been disabled for a
long time. Since only a limited configuration is supported for
building with Xcode (pretty much just LLVM and Swift, with only a
macOS standard library), it doesn't make sense to base it on the
regular incremental preset. Pare it down to what's most important to
keep working in hopes of turning the bot back on.

Author: jrose-apple

utils/build-presets.ini

@@ -346,12 +346,18 @@ install-llbuild
 install-swiftpm
 install-libcxx
 
+
 [preset: buildbot_incremental,tools=RA,stdlib=RA,xcode]
-mixin-preset=buildbot_incremental,tools=RA,stdlib=RA
-build-subdir=buildbot_incremental_xcode
+mixin-preset=buildbot_incremental_base
 
+build-subdir=buildbot_incremental_xcode
 xcode
-dash-dash
+libcxx
+
+# Build Release without debug info, because it is faster to build.
+release
+assertions
+
 # We do not support building cross compiled stdlibs on OS X with Xcode. So only
 # build the OS X SDK.
 skip-build-ios
@@ -363,12 +369,12 @@ skip-test-watchos
 stdlib-deployment-targets=macosx-x86_64
 swift-primary-variant-sdk=OSX
 swift-primary-variant-arch=x86_64
-skip-build-llbuild
-skip-test-llbuild
-skip-build-swiftpm
-skip-test-swiftpm
-skip-build-playgroundsupport
-skip-test-playgroundsupport
+
+# CMark's tests aren't set up to handle the config-specific build directories
+# that CMake uses for Xcode. Rather than change CMark (which is 99% the same
+# as upstream), we'll just skip testing it.
+skip-test-cmark
+
 
 # This preset is used by CI to test swift-corelibs-xctest.
 [preset: buildbot_incremental,tools=RA,stdlib=RA,XCTest]