* I can't seem to get alloc to work with Embassy stm32 any ideas?

```
use cortex_m_alloc::CortexMHeap;

// Heap allocator
#[global_allocator]
pub static ALLOCATOR: CortexMHeap = CortexMHeap::empty();

// ...snip
// This crashes on `to_string()`
        if let Some(dt) = dt_opt {
            // let dt_rfc2822 = dt.to_rfc2822();
            // let now = dt_rfc2822.as_str();
            let now = dt.timestamp().to_string();
            info!("loop: Got RTC! {=str}", now);
        }

0.017211 INFO  Got RTC! 1589538615
└─ stm32h747_async_quickstart::____embassy_main_task::{async_fn#0} @ src/main.rs:105 
20.634704 INFO  low
└─ stm32h747_async_quickstart::____embassy_main_task::{async_fn#0} @ src/main.rs:113 
20.934722 INFO  vrefint: 24575
└─ stm32h747_async_quickstart::____embassy_main_task::{async_fn#0} @ src/main.rs:118 
20.934722 INFO  measured: 14930
└─ stm32h747_async_quickstart::____embassy_main_task::{async_fn#0} @ src/main.rs:120 
45.742980 ERROR panicked at library/alloc/src/alloc.rs:418:13:
memory allocation of 10 bytes failed
└─ panic_probe::print_defmt::print @ /Users/mdesilva/.cargo/registry/src/index.crates.io-6f17d22bba15001f/panic-probe-0.3.1/src/lib.rs:104 

```