reuse config/build_config.txt for all bootstrap scripts (posix + windows + ci); use build_all.bat in 1 CI, fix bug in build_all.bat (#17899)

* reuse config/build_config.txt for all bootstrap scripts (posix + windows + ci)
* ci_docs: use build_all.bat in CI (just in that pipeline) to ensure it keeps working
* fixup
* fix pre-existing bug in build_all.bat
* fixup
* cp => copy /y
* auto-generate build_all.bat, build_all.sh
* fixup

.github/workflows/ci_docs.yml

@@ -70,13 +70,21 @@ jobs:
         shell: bash
         run: echo "${{ github.workspace }}/bin" >> "${GITHUB_PATH}"
 
-      - name: 'Build csourcesAny'
+      - name: 'Build csourcesAny (posix)'
+        # this would work on windows and other CI use this on windows,
+        # but we ensure here that `ci/build_autogen.bat` keeps working on windows.
+        if: runner.os != 'Windows'
         shell: bash
         run: . ci/funs.sh && nimBuildCsourcesIfNeeded CC=gcc
           # was previously using caching via `actions/cache@v1` but this wasn't
           # used in other CI pipelines and it's unclear the added complexity
           # was worth the saving; can be revisited if needed.
 
+      - name: 'Build csourcesAny (windows)'
+        if: runner.os == 'Windows'
+        shell: cmd
+        run: ci/build_autogen.bat
+
       - name: 'Build koch'
         shell: bash
         run: nim c koch