meson: qga: do not use deprecated meson.build_root()

The function will return the build root of the parent project if called from a
subproject; that is irrelevant for QEMU's usage but rarely desirable, and
therefore the function was deprecated and replaced by two functions
project_build_root() and global_build_root().  Replace it with the former.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

qga/meson.build

@@ -125,7 +125,7 @@ if targetos == 'windows'
                               wixl, '-o', '@OUTPUT0@', '@INPUT0@',
                               qemu_ga_msi_arch[cpu],
                               qemu_ga_msi_vss,
-                              '-D', 'BUILD_DIR=' + meson.build_root(),
+                              '-D', 'BUILD_DIR=' + meson.project_build_root(),
                               '-D', 'BIN_DIR=' + glib.get_variable('bindir'),
                               '-D', 'QEMU_GA_VERSION=' + config_host['QEMU_GA_VERSION'],
                               '-D', 'QEMU_GA_MANUFACTURER=' + config_host['QEMU_GA_MANUFACTURER'],