Build fails on aarch64 after error: Assignment: Cannot convert from `int64' to `time_t'

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What Happened?

I'm building calendar on an aarch64 environment. Compiling fails after these messages:

libgdata.vapi:2038.3-2038.27: warning: Creation method of abstract class cannot be public.
                public Parsable.from_json (GLib.Type parsable_type, string json, int length) throws GLib.Error;
                ^^^^^^^^^^^^^^^^^^^^^^^^^
libgdata.vapi:2041.3-2041.26: warning: Creation method of abstract class cannot be public.
                public Parsable.from_xml (GLib.Type parsable_type, string xml, int length) throws GLib.Error;
                ^^^^^^^^^^^^^^^^^^^^^^^^
../core/Services/Calendar/Util/ECalComponent.vala:75.16-75.25: error: Assignment: Cannot convert from `int64' to `time_t'
        time_t start_unix = start_time.as_timet_with_zone (system_timezone);
               ^^^^^^^^^^
../core/Services/Calendar/Util/ECalComponent.vala:76.16-76.23: error: Assignment: Cannot convert from `int64' to `time_t'
        time_t end_unix = end_time.as_timet_with_zone (system_timezone);
               ^^^^^^^^
../core/Services/Calendar/Util/ICalTime.vala:57.20-57.77: warning: `GLib.TimeZone.new' has been deprecated since 2.68. Use TimeZone.identifier
../core/Services/Calendar/Util/ICalTime.vala:61.20-61.43: warning: `GLib.TimeZone.new' has been deprecated since 2.68. Use TimeZone.identifier
Compilation failed: 2 error(s), 4 warning(s)
ninja: subcommand failed

Steps to Reproduce

1. Chroot into an aarch64 environment
2. Install all build-tools and dependencies listed in the README.md
3. Clone the repo
4. cd into the clone
5. optional: checkout 6.1.0
6. meson build --prefix=/usr
7. cd build
8. ninja

Step 7 fails after the messages mentioned above.

Expected Behavior

I expected to end up with an executable of calendar for aarch64 architecture.

OS Version

Other Linux

Software Version

Latest release (I have run all updates)

Log Output

No response

Hardware Info

The environment is an aarch64 environment with Alpine Linux, created using qemu, hosted on a amd64 machine.