Work on check-macos: Enable building on macOS 26.

Suggested by Collin Funk.

Author: bhaible

.github/workflows/many-platforms.yml

@@ -288,7 +288,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [macos-13, macos-14, macos-15]
+        os: [macos-13, macos-14, macos-15, macos-26]
     runs-on: ${{ matrix.os }}
     steps:
       # This is needed because we run a script stored in this repository.
@@ -309,7 +309,7 @@ jobs:
           pwd
           export CPPFLAGS="-I$HOME/include -I${HOMEBREW_PREFIX-/usr/local}/opt/gettext/include -I${HOMEBREW_PREFIX-/usr/local}/opt/libiconv/include -Wall"
           export LDFLAGS="-L$HOME/lib -L${HOMEBREW_PREFIX-/usr/local}/opt/gettext/lib -L${HOMEBREW_PREFIX-/usr/local}/opt/libiconv/lib"
-          ./build-on.sh '${{ env.package }}' '' 'make' ${{ (matrix.os == 'macos-14' || matrix.os == 'macos-15') && 'brew install gettext gmp openssl@3' || 'brew install gmp openssl@3' }}
+          ./build-on.sh '${{ env.package }}' '' 'make' ${{ (matrix.os == 'macos-14' || matrix.os == 'macos-15' || matrix.os == 'macos-26') && 'brew install gettext gmp openssl@3' || 'brew install gmp openssl@3' }}
       # Doc: https://docs.github.com/en/actions/using-workflows/storing-workflow-data-as-artifacts
       #      https://github.com/actions/upload-artifact?tab=readme-ov-file#usage
       - if: ${{ always() }}