Another attempt with cfitsio and macosx....

.github/workflows/test_macos.yml

@@ -3,7 +3,8 @@ name: MacOS Tests
 on: [push, pull_request]
 
 env:
-  RUST_BACKTRACE: 1  
+  RUST_BACKTRACE: 1
+  PKG_CONFIG_PATH: "/Users/runner/work/mwalib/mwalib/cfitsio-3.49/lib/pkgconfig"
 
 jobs:
   test_macos:
@@ -22,10 +23,21 @@ jobs:
           toolchain: stable
           override: true
 
-    - name: Uninstall curl and install cfitsio
+    - name: Build cfitsio
       run: |
-          brew uninstall --ignore-dependencies curl
-          brew install cfitsio
+          # Install dependencies
+          curl "https://heasarc.gsfc.nasa.gov/FTP/software/fitsio/c/cfitsio-3.49.tar.gz" -o cfitsio.tar.gz
+          tar -xf cfitsio.tar.gz
+          rm cfitsio.tar.gz
+          cd cfitsio-3.49
+          # Enabling SSE2/SSSE3 could cause portability problems, but it's unlikely that anyone
+          # is using such a CPU...
+          # https://stackoverflow.com/questions/52858556/most-recent-processor-without-support-of-ssse3-instructions
+          # Disabling curl just means you cannot fits_open() using a URL.
+          CFLAGS="-O3" ./configure --enable-reentrant --enable-sse2 --enable-ssse3 --disable-curl          
+          make shared
+          sudo make install
+          cd ..
 
     - name: Run tests
       run: MWALIB_LINK_STATIC_CFITSIO=1 cargo test --release --verbose