Add support for Qt 6.1+

Qt 6.1 moved the location of some binaries from QT_HOST_BINS to
QT_HOST_LIBEXECS as noted in the changelog:

c515ee178f Move build tools to libexec instead of the bin dir
- Tools that are called by the build system and are unlikely to be
called by the user are now installed to the libexec directory.

https://code.qt.io/cgit/qt/qtreleasenotes.git/tree/qt/6.1.0/release-note.txt

It's possible to help the 'qt' module find the tools by adding Qt's
libexec directory to the PATH environment variable, but this manual
workaround is not ideal.

To compensate, meson now needs to look for moc, rcc, uic, etc. in
QT_HOST_LIBEXECS as well as QT_HOST_BINS.

Co-authored-by: Stefan Hajnoczi <stefanha@jammr.net>

mesonbuild/dependencies/qt.py

@@ -69,6 +69,12 @@ def get_qmake_host_bins(qvars: T.Dict[str, str]) -> str:
     return qvars['QT_INSTALL_BINS']
 
 
+def get_qmake_host_libexecs(qvars: T.Dict[str, str]) -> T.Optional[str]:
+    if 'QT_HOST_LIBEXECS' in qvars:
+        return qvars['QT_HOST_LIBEXECS']
+    return qvars.get('QT_INSTALL_LIBEXECS')
+
+
 def _get_modules_lib_suffix(version: str, info: 'MachineInfo', is_debug: bool) -> str:
     """Get the module suffix based on platform and debug type."""
     suffix = ''
@@ -118,6 +124,7 @@ class _QtBase:
     link_args: T.List[str]
     clib_compiler: 'Compiler'
     env: 'Environment'
+    libexecdir: T.Optional[str] = None
 
     def __init__(self, name: str, kwargs: T.Dict[str, T.Any]):
         self.qtname = name.capitalize()
@@ -277,6 +284,7 @@ class QmakeQtDependency(_QtBase, ConfigToolDependency, metaclass=abc.ABCMeta):
         libdir = qvars['QT_INSTALL_LIBS']
         # Used by qt.compilers_detect()
         self.bindir = get_qmake_host_bins(qvars)
+        self.libexecdir = get_qmake_host_libexecs(qvars)
 
         # Use the buildtype by default, but look at the b_vscrt option if the
         # compiler supports it.
@@ -353,6 +361,7 @@ class QmakeQtDependency(_QtBase, ConfigToolDependency, metaclass=abc.ABCMeta):
             self.is_found = True
             # Used by self.compilers_detect()
             self.bindir = get_qmake_host_bins(qvars)
+            self.libexecdir = get_qmake_host_libexecs(qvars)
 
     def log_info(self) -> str:
         return 'qmake'

mesonbuild/modules/qt.py

@@ -131,6 +131,8 @@ class QtBaseModule(ExtensionModule):
             for b in self.tools:
                 if qt_dep.bindir:
                     yield os.path.join(qt_dep.bindir, b), b
+                if qt_dep.libexecdir:
+                    yield os.path.join(qt_dep.libexecdir, b), b
                 # prefer the <tool>-qt<version> of the tool to the plain one, as we
                 # don't know what the unsuffixed one points to without calling it.
                 yield f'{b}-qt{qt_dep.qtver}', b