Don't initialize the other CMAKE_<LANG>_COMPILER_PREDEFINES_COMMAND
variables.
The only language variant that is used is
CMAKE_CXX_COMPILER_PREDEFINES_COMMAND, and the other language variants
contained invalid, namely C++-specific commands.
Fixes: #23968
The CMake support for Android assumes cross-compilation using the NDK,
so stub out that Android NDK support and use the Linux support that's
already invoked. Set CMAKE_HOST_SYSTEM_NAME to "Android", rather than
"Linux".
Issue: #19840
The NDK build system now uses only a single toolchain in
<ndk>/toolchains/llvm/prebuilt/<host>
Its compilers are always `bin/{clang,clang++}` and its binutils are
always `bin/<triple>-*`. It is a standalone toolchain:
* The Anrdoid API level is specified at the end of `--target=`.
* The standard library may be specified via `-stdlib=`.
* No need to pass system includes or libraries explicitly.
* No need to pass `--sysroot` or `-gcc-toolchain`.
Teach CMake to recognize NDK versions that have a unified
toolchain with its own sysroot and use the above approach.
Fixes: #18739
When we set `CMAKE_<LANG>_COMPILER_TARGET` to the Android target
architecture, add it to `CMAKE_<LANG>_COMPILER_PREDEFINES_COMMAND` also.
This is needed to make moc predefines aware of `__ANDROID__`.
Fixes: #18425
Per-source copyright/license notice headers that spell out copyright holder
names and years are hard to maintain and often out-of-date or plain wrong.
Precise contributor information is already maintained automatically by the
version control tool. Ultimately it is the receiver of a file who is
responsible for determining its licensing status, and per-source notices are
merely a convenience. Therefore it is simpler and more accurate for
each source to have a generic notice of the license name and references to
more detailed information on copyright holders and full license terms.
Our `Copyright.txt` file now contains a list of Contributors whose names
appeared source-level copyright notices. It also references version control
history for more precise information. Therefore we no longer need to spell
out the list of Contributors in each source file notice.
Replace CMake per-source copyright/license notice headers with a short
description of the license and links to `Copyright.txt` and online information
available from "https://cmake.org/licensing". The online URL also handles
cases of modules being copied out of our source into other projects, so we
can drop our notices about replacing links with full license text.
Run the `Utilities/Scripts/filter-notices.bash` script to perform the majority
of the replacements mechanically. Manually fix up shebang lines and trailing
newlines in a few files. Manually update the notices in a few files that the
script does not handle.
The Android NDK source repository at
https://android.googlesource.com/platform/ndk.git
has `<ndk>/build/core/toolchains/*/setup.mk` files that store tables of
information for their build system. Add an equivalent file for each
compiler/abi combination.
Commonly used Android toolchain files that pre-date CMake upstream
support may need to be updated to work with our new functionality.
They typically set CMAKE_SYSTEM_VERSION to 1, so detect that and
skip our upstream Android settings. When such toolchain files are
updated to account for our upstream support, they can then set
CMAKE_SYSTEM_VERSION to a valid Android API and get new behavior.
Support for NVIDIA Nsight Tegra Visual Studio Edition was previously
implemented in the CMake VS IDE generators. Avoid interfering with
that functionality for now. Later we may try to integrate this.
