Try fixing LDFLAGS:

Author: matthew-brett

.github/workflows/build.yml

@@ -34,20 +34,20 @@ jobs:
 
       - name: Set env variables
         run: |
+          echo "START_DIR=$PWD" >> $env:GITHUB_ENV
           $BITS = ${{ matrix.BUILD_BITS }}
           echo "BUILD_BITS=$BITS" >> $env:GITHUB_ENV
           # For interpretation of MSYSTEM, see:
           # https://sourceforge.net/p/msys2/discussion/general/thread/b7dfdac8/#3939
           if ($BITS -eq 32) {
             echo "PLAT=i686" >> $env:GITHUB_ENV
             echo "MSYSTEM=MINGW32" >> $env:GITHUB_ENV
-            echo "LDFLAGS='-static -static-libgcc'" >> $env:GITHUB_ENV
+            echo "LDFLAGS=-static -static-libgcc" >> $env:GITHUB_ENV
           } else {
             echo "PLAT=x86_64" >> $env:GITHUB_ENV
             echo "MSYSTEM=UCRT64" >> $env:GITHUB_ENV
-            echo "LDFLAGS='-lucrt -static -static-libgcc'" >> $env:GITHUB_ENV
+            echo "LDFLAGS=-lucrt -static -static-libgcc" >> $env:GITHUB_ENV
           }
-          echo "START_DIR=$PWD" >> $env:GITHUB_ENV
           if ( ${{ matrix.INTERFACE64 }} -eq 1 ) {
             echo "INTERFACE64=1" >> $env:GITHUB_ENV
           }