rename hex -> output

using generic term 'output', because for samx32,
output is .bin format and not .hex

Signed-off-by: Arnav Gupta <championswimmer@gmail.com>

Author: championswimmer

platform.txt

@@ -69,7 +69,7 @@ recipe.c.combine.pattern="{compiler.path}{compiler.c.elf.cmd}" {compiler.c.elf.f
 recipe.objcopy.eep.pattern=
 
 ## Create hex
-recipe.objcopy.hex.pattern="{compiler.path}{compiler.elf2hex.cmd}" {compiler.elf2hex.flags} {compiler.elf2hex.extra_flags} "{build.path}/{build.project_name}.elf" "{build.path}/{build.project_name}.bin"
+recipe.objcopy.output.pattern="{compiler.path}{compiler.elf2hex.cmd}" {compiler.elf2hex.flags} {compiler.elf2hex.extra_flags} "{build.path}/{build.project_name}.elf" "{build.path}/{build.project_name}.bin"
 
 ## Compute size
 recipe.size.pattern="{compiler.path}{compiler.size.cmd}" -A "{build.path}/{build.project_name}.elf"