configury update & bump VERSION to 0.9.28rc

configure:
- option --targetos=... for cross build
- cleanup

win32/build-tcc.bat:
- option -b <bindir>
- make 'libtcc1.a' and cross-prefix-libtcc1.a
  (same convention as with makefile)

Makefile:
- streamline tcov-tests, help, etc.

workflow/build.xml: simplify
- using "windows-2019" runner (instead of windows-latest)
  because its msys seems more complete and has no problems
  with the 96_nodata_wanted.test either.

Changelog,TODO,USES,tcc-doc.texi: update

.github/workflows/build.yml

@@ -1,68 +1,32 @@
 name: build and run tests
+
 on:
   push:
     branches: [ mob ]
-  pull_request:
-    branches: [ mob ]
+
 jobs:
-  build-release-linux-i686-amd64:
-    name: tinycc master linux/amd64
+  test-x86_64-linux:
     runs-on: ubuntu-20.04
     steps:
-    - uses: actions/checkout@v2
-    - name: Install dependencies
-      run: sudo apt-get install -y
-        gcc
-    # see what's available in /usr/bin
-    - name: see what's available
-      run: ls -l /usr/bin
-    # build project amd64
-    - name: build amd64
-      run: |
-        ./configure
-        make
-    # run tests
-    - name: run test_exs amd64
-      run: |
-        make test
+    - uses: actions/checkout@v3
+    - name: make & test tcc
+      run: ./configure && make && make test -k
 
-  build-release-osx-amd64:
-    name: tinycc master osx/amd64
+  test-x86_64-osx:
     runs-on: macos-11
     steps:
-    - uses: actions/checkout@v2
-    # see what's available in /usr/bin
-    - name: see what's available
-      run: ls -l /usr/bin
-    # build project amd64
-    - name: build amd64
-      run: |
-        ./configure
-        make
-    # run tests
-    - name: run test_exs amd64
-      run: |
-        make test
+    - uses: actions/checkout@v3
+    - name: make & test tcc
+      run: ./configure && make && make test -k
 
-  build-release-windows-amd64-on-windows:
-    name: tinycc master windows/amd64 on Windows
-    runs-on: windows-latest
+  test-x86_64-win32:
+    runs-on: windows-2019
     steps:
-    - uses: actions/checkout@v2
-    - uses: msys2/setup-msys2@v2
-    # build project amd64
-    - name: build amd64
+    - uses: actions/checkout@v3
+    - name: make & test tcc
+      shell: cmd
       run: |
-        msys2 -c './configure'
-        make
-    # silency failing tests
-    - name: silence 96_nodata_wanted
-      run: |
-        pushd .\tests\tests2
-        Get-Content .\96_nodata_wanted.expect -TotalCount 2 | Out-File .\96_nodata_wanted.expect2 -Encoding default
-        mv .\96_nodata_wanted.expect2 .\96_nodata_wanted.expect -force
-        popd
-    # run tests
-    - name: run test_exs amd64
-      run: |
-        make test
+        set MSYS2_PATH_TYPE=inherit
+        set MSYSTEM=MINGW64
+        set CHERE_INVOKING=yes
+        C:\msys64\usr\bin\bash -l -c "./configure && make && make test -k"