fix: Update cargo's config to use the new linker parameter (#100)

Since rust v1.74, the linker can be selected without using rustflags.
This plays nicer with `RUSTFLAGS`.

.cargo/config.toml

@@ -5,8 +5,8 @@
 runner = "probe-rs run --chip RP2040 --protocol swd"
 # runner = "elf2uf2-rs -d"
 
+linker = "flip-link"
 rustflags = [
-  "-C", "linker=flip-link",
   "-C", "link-arg=--nmagic",
   "-C", "link-arg=-Tlink.x",
   "-C", "link-arg=-Tdefmt.x",

cargo-generate/config.toml

@@ -15,8 +15,8 @@
       runner = "{{ flash_method_custom }}"
     {%- endif -%}
 {%- endcase %}
+linker = "flip-link"
 rustflags = [
-  "-C", "linker=flip-link",
   "-C", "link-arg=--nmagic",
   "-C", "link-arg=-Tlink.x",
   "-C", "link-arg=-Tdefmt.x",