CI: repair the worflow definition

The `workflow_dispatch` event is used for triggering manual jobs,
`workflow_jobs` is for consumption of other jobs.

Correct a typo in the checkout action name.

Disable the Windows ARM64 build target as cross-compilation does not
currently work.
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 15d0f5b..55e1499 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -4,20 +4,21 @@
   pull_request:
     branches:
       - master
-  workflow_run:
+  workflow_dispatch:
 
 jobs:
   windows:
     runs-on: windows-latest
 
     strategy:
+      fail-fast: false
       matrix:
-        arch: ["Win32", "x64", "ARM64"]
+        arch: ["Win32", "x64"] # "ARM64"
 
     steps:
-      - uses: actions/echeckout@v2
+      - uses: actions/checkout@v2
       - name: configure
-        run: cmake -B build -D CMAKE_BUILD_TYPE=Debug -G "Visual Studio 16 2019" -A ${{ matrix.arch }} -S .
+        run: cmake -B build -D CMAKE_BUILD_TYPE=Debug -G "Visual Studio 16 2019" -A ${{ matrix.arch }} -S . -D CMAKE_CXX_FLAGS_Debug="/MTd /Zi /Ob0 /Od /RTC1"
       - name: build
         run: cmake --build build --config Debug
       - name: test
@@ -33,7 +34,7 @@
           - { cflags: "-fmodules", cxxflags: "-fmodules" }
 
     steps:
-      - uses: actions/echeckout@v2
+      - uses: actions/checkout@v2
       - name: configure
         run: cmake -B build -D CMAKE_BUILD_TYPE=Debug -D CMAKE_C_FLAGS=${{ matrix.cflags }} -D CMAKE_CXX_FLAGS=${{ matrix.cxxflags }} -S .
       - name: build
@@ -51,7 +52,7 @@
           - { CC: clang, CXX: clang++ }
 
     steps:
-      - uses: actions/echeckout@v2
+      - uses: actions/checkout@v2
       - name: configure
         run: cmake -B build -D CMAKE_BUILD_TYPE=Debug -S .
         env: