[build] Add a new flag to disable cross-compiling the compiler

This is useful when building cross-compilation toolchains where you want the
stdlib and corelibs cross-compiled but don't want the Swift compiler
cross-compiled too with '--cross-compile-hosts'. This pull demonstrates using the
new flag for the Android build presets.

Author: finagolfin

utils/build-presets.ini

@@ -872,7 +872,7 @@ mixin-preset=
     buildbot_linux
     mixin_buildbot_linux,no_test
 
-[preset: buildbot_linux_crosscompile_android,tools=RA,stdlib=RD,build]
+[preset: buildbot_linux_crosscompile_android_generic,tools=RA,stdlib=RD,build]
 mixin-preset=
     mixin_lightweight_assertions,no-stdlib-asserts
     mixin_linux_install_components_with_clang
@@ -889,6 +889,7 @@ lit-args=-v --time-tests
 build-ninja
 libicu
 libcxx
+xctest
 
 android
 android-ndk=%(ndk_path)s
@@ -899,6 +900,10 @@ android-icu-i18n=%(arm_dir)s/libicui18nswift.so
 android-icu-i18n-include=%(arm_dir)s/icu/source/i18n
 android-icu-data=%(arm_dir)s/libicudataswift.so
 
+cross-compile-deps-path=%(prebuilt_path)s
+cross-compile-build-swift-tools=0
+llvm-ninja-targets-for-cross-compile-hosts=help
+
 build-swift-static-stdlib
 build-swift-static-sdk-overlay
 build-swift-stdlib-unittest-extra
@@ -914,20 +919,29 @@ host-test
 extra-cmake-options=-DSWIFT_ENABLE_LLD_LINKER:BOOL=OFF
 
 install-prefix=/usr
-install-llvm
 install-swift
 install-libicu
 install-libcxx
+install-libdispatch
+install-foundation
+install-xctest
 
 skip-test-linux
 skip-build-benchmarks
 
 reconfigure
 
+[preset: buildbot_linux_crosscompile_android,tools=RA,stdlib=RD,build]
+mixin-preset=buildbot_linux_crosscompile_android_generic,tools=RA,stdlib=RD,build
+
+android-arch=armv7
+cross-compile-hosts=android-armv7
+
 [preset: buildbot_linux_crosscompile_android,tools=RA,stdlib=RD,build,aarch64]
-mixin-preset=buildbot_linux_crosscompile_android,tools=RA,stdlib=RD,build
+mixin-preset=buildbot_linux_crosscompile_android_generic,tools=RA,stdlib=RD,build
 
 android-arch=aarch64
+cross-compile-hosts=android-aarch64
 
 # Ubuntu 18.04 preset for backwards compat and future customizations.
 [preset: buildbot_linux_1804]

utils/build-script-impl

@@ -230,6 +230,7 @@ KNOWN_SETTINGS=(
     cross-compile-with-host-tools                 ""                "set to use the clang we build for the host to then build the cross-compile hosts"
     cross-compile-install-prefixes                ""                "semicolon-separated list of install prefixes to use for the cross-compiled hosts. The list expands, so if there are more cross-compile hosts than prefixes, unmatched hosts use the last prefix in the list"
     cross-compile-deps-path                       ""                "path for CMake to look for cross-compiled library dependencies, such as libXML2"
+    cross-compile-build-swift-tools               "1"               "set to 1 to cross-compile the Swift host tools, like the Swift compiler"
     skip-merge-lipo-cross-compile-tools           ""                "set to skip running merge-lipo after installing cross-compiled host Swift tools"
     coverage-db                                   ""                "If set, coverage database to use when prioritizing testing"
     skip-local-host-install                       ""                "If we are cross-compiling multiple targets, skip an install pass locally if the hosts match"
@@ -1909,6 +1910,12 @@ for host in "${ALL_HOSTS[@]}"; do
                     cmake_options=(
                         "${cmake_options[@]}"
                         -DLLVM_TABLEGEN=$(build_directory "${LOCAL_HOST}" llvm)/bin/llvm-tblgen
+                        -DSWIFT_INCLUDE_TOOLS:BOOL=$(true_false "${CROSS_COMPILE_BUILD_SWIFT_TOOLS}")
+                    )
+                else
+                    cmake_options=(
+                        "${cmake_options[@]}"
+                        -DSWIFT_INCLUDE_TOOLS:BOOL=$(true_false "${BUILD_SWIFT_TOOLS}")
                     )
                 fi
 
@@ -1963,7 +1970,6 @@ for host in "${ALL_HOSTS[@]}"; do
                     -DSWIFT_NATIVE_LLVM_TOOLS_PATH:STRING="${native_llvm_tools_path}"
                     -DSWIFT_NATIVE_CLANG_TOOLS_PATH:STRING="${native_clang_tools_path}"
                     -DSWIFT_NATIVE_SWIFT_TOOLS_PATH:STRING="${native_swift_tools_path}"
-                    -DSWIFT_INCLUDE_TOOLS:BOOL=$(true_false "${BUILD_SWIFT_TOOLS}")
                     -DSWIFT_BUILD_REMOTE_MIRROR:BOOL=$(true_false "${BUILD_SWIFT_REMOTE_MIRROR}")
                     -DSWIFT_STDLIB_SIL_DEBUGGING:BOOL=$(true_false "${BUILD_SIL_DEBUGGING_STDLIB}")
                     -DSWIFT_CHECK_INCREMENTAL_COMPILATION:BOOL=$(true_false "${CHECK_INCREMENTAL_COMPILATION}")

utils/build_swift/tests/build_swift/test_presets.py

@@ -46,6 +46,7 @@
     'swift_install_destdir': '/tmp/install/swift',
     'symbols_package': '/path/to/symbols/package',
     'ndk_path': '/path/to/ndk',
+    'prebuilt_path': '/path/to/prebuilt_library_dependencies',
     'arm_dir': '/path/to/arm',
     'toolchain_path': '/tmp/toolchain',
 }