Additional MacOS fixes

.github/workflows/R-CMD-check.yaml

@@ -29,6 +29,34 @@ jobs:
       R_KEEP_PKG_SOURCE: yes
 
     steps:
+      - name: Install X11 dependencies on MacOS
+        if: runner.os == 'macOS'
+        run: brew install --cask xquartz
+        shell: bash
+
+      - name: Install deps on MacOS
+        if: runner.os == 'macOS'
+        run: |
+          brew install cairo
+          brew install libgit2
+          brew install udunits
+        shell: bash
+
+      - name: Link gfortran on MacOS
+        if: runner.os == 'macOS'
+        run: |
+          sudo ln -s /usr/local/bin/gfortran-10 /usr/local/bin/gfortran
+          sudo mkdir /usr/local/gfortran
+          sudo ln -s /usr/local/gfortran-10 /usr/local/gfortran
+        shell: bash
+
+      - name: Create Makevars for Fortran linking options on macOS
+        if: runner.os == 'macOS'
+        run: |
+          try(dir.create("~/.R"))
+          writeLines(c("GCCBASE:=$(shell brew --prefix gcc)","FLIBS=-L$(GCCBASE)/lib/gcc/10/lib -lm",""),"~/.R/Makevars")
+        shell: Rscript {0}
+
       - uses: actions/checkout@v2
 
       - uses: r-lib/actions/setup-pandoc@v1