add check for void for microzig.hal (#112)

* add check for void for microzig.hal

* modify github actions to run on every push

.github/workflows/build.yml

@@ -1,11 +1,6 @@
 name: Build
 on:
   push:
-    branches: [ main ]
-  pull_request:
-    branches: [ main ]
-  schedule:
-    - cron: "0 0 * * *"
 
 jobs:
   build:

src/modules/cpus/cortex-m.zig

@@ -84,7 +84,7 @@ fn is_valid_field(field_name: []const u8) bool {
 
 const VectorTable = if (@hasDecl(root, "microzig_options") and @hasDecl(root.microzig_options, "VectorTable"))
     root.microzig_options.VectorTable
-else if (@hasDecl(microzig.hal, "VectorTable"))
+else if (microzig.hal != void and @hasDecl(microzig.hal, "VectorTable"))
     microzig.hal.VectorTable
 else
     microzig.chip.VectorTable;