fix call to matrix.os

Author: Artur-man

.Rbuildignore

@@ -1 +1,3 @@
 .circleci/
+^.*\.Rproj$
+^\.Rproj\.user$

.github/workflows/main.yml

@@ -47,7 +47,7 @@ jobs:
         which R
         R --version
     - name: Configuration Information (Windows)
-      if: startsWith(matrix.config.os, 'windows')
+      if: startsWith(matrix.os, 'windows')
       shell: pwsh
       run: |
         New-Item -ItemType Directory -Force -Path "$env:R_LIBS" | Out-Null
@@ -60,7 +60,7 @@ jobs:
       run: |
         R -e "install.packages(c('remotes'), lib=c('${R_LIBS}'), repo='https://cloud.r-project.org/')"
     - name: Install R packages (Windows)
-      if: startsWith(matrix.config.os, 'windows')
+      if: startsWith(matrix.os, 'windows')
       shell: pwsh
       run: |
         Rscript -e "lib <- Sys.getenv('R_LIBS'); lib <- normalizePath(lib, winslash='/', mustWork=FALSE); dir.create(lib, recursive=TRUE, showWarnings=FALSE); install.packages('remotes', lib=lib, repos='https://cloud.r-project.org/')"
@@ -73,7 +73,7 @@ jobs:
       env:
         ITK_GLOBAL_DEFAULT_NUMBER_OF_THREADS: 2
     - name: Build and test (Windows)
-      if: startsWith(matrix.config.os, 'windows')
+      if: startsWith(matrix.os, 'windows')
       shell: pwsh
       env:
         ITK_GLOBAL_DEFAULT_NUMBER_OF_THREADS: 2