Fix spelling of 'available'

Signed-off-by: NZygmunt Krynicki <zygmunt.krynicki@huawei.com>
Change-Id: I8880edddd2194ab1cdcf01c7d5c3a6b100d3178a

config/BUILDCONFIG.gn

@@ -21,7 +21,7 @@ if (target_cpu == "") {
   target_cpu = board_cpu
 }
 
-# Only gcc avaiable for liteos_m.
+# Only gcc available for liteos_m.
 if (ohos_kernel_type == "liteos_m" || ohos_kernel_type == "linux") {
   use_board_toolchain = true
 }