Simplify some conditionals

etc/kaleidoscope-builder.conf

@@ -15,18 +15,16 @@ if [[  -z "${ARCH}" && -n "${FQBN}" ]]; then
    ARCH=$(echo "${FQBN}" | sed -n -e 's/^[^:]\+:\([^:]\+\).*/\1/p')
 fi
 
+: "${ARCH:=avr}"
+
 if [ "${ARCH}" = "virtual" ]; then
     : "${FQBN:=keyboardio:virtual:${BOARD}}"
     : "${COMPILER_PATH:=/usr/bin}" 
 
     COMPILER_PREFIX=""
-else
-   ARCH="avr"
 fi
 
-if [ -z "${FQBN}" ]; then
-   : "${FQBN:=keyboardio:avr:${BOARD}}"
-fi
+: "${FQBN:=keyboardio:${ARCH}:${BOARD}}"
 
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