cargo: include .cargo/config in source control tied to arm-none-eabi-

Checking in this config fragment is mentioned as being something that
could be acceptable in the cargo documentation.  This prevents non-gcc
linkers for builds of the Zinc examples.  I think this is likely
an acceptable tradeoff, at least in the short term.

Signed-off-by: Paul Osborne <[email protected]>

Author: posborne

.cargo/config

@@ -0,0 +1,11 @@
+[target.thumbv6-none-eabi]
+linker = "arm-none-eabi-gcc"
+ar = "arm-none-eabi-ar"
+
+[target.thumbv7m-none-eabi]
+linker = "arm-none-eabi-gcc"
+ar = "arm-none-eabi-ar"
+
+[target.thumbv7em-none-eabi]
+linker = "arm-none-eabi-gcc"
+ar = "arm-none-eabi-ar"

.gitignore

@@ -3,7 +3,6 @@
 .DS_Store
 Cargo.lock
 target
-.cargo
 *.o
 *.bin
 *.lst