tests/spi: Fix for samr21-xpro and other non-atomic boards

tests/spi/Cargo.toml

@@ -11,6 +11,13 @@ crate-type = ["staticlib"]
 panic = "abort"
 
 [dependencies]
-riot-wrappers = { path = "../..", features = [ "set_panic_handler", "panic_handler_format" ] }
+# critical-section: We don't *use* this, but the embedded-hal-bus crate also contains variants that rely on critical sections, so we have to enable it.
+riot-wrappers = { path = "../..", features = [ "set_panic_handler", "panic_handler_format", "provide_critical_section_1_0" ] }
 embedded-hal = "1"
 embedded-hal-bus = "0.2.0"
+
+# Actually this is only required on samr21 and other non-atomic platforms to
+# make the static_cell work, but for sake of setup simplicity we'll keep this
+# enabled everywhere. (A better solution would be to have the RIOT build system
+# managed crates provide this dependency on platforms where it is needed).
+portable-atomic = { version = "1.6", default-features = false, features = [ "critical-section" ] }