Switch CI to grab Ipopt from github.com/coin-or rather than coin-or.org

- Ipopt Matlab inferface build failing due to coin-or.org being down.

.github/workflows/continuous-integration.yml

@@ -47,8 +47,8 @@ jobs:
       run: |
         export PKG_CONFIG_PATH=$HOME/install/lib/pkgconfig
         mkdir $HOME/build
-        curl -SL https://www.coin-or.org/download/source/Ipopt/Ipopt-${IPOPT_VER}.tgz | tar -xzC $HOME/build
-        mv $HOME/build/Ipopt-${IPOPT_VER}/Ipopt/contrib/MatlabInterface $HOME/build/ipopt
+        curl -SL https://github.com/coin-or/Ipopt/archive/releases/${IPOPT_VER}.tar.gz | tar -xzC $HOME/build
+        mv $HOME/build/Ipopt-releases-${IPOPT_VER}/Ipopt/contrib/MatlabInterface $HOME/build/ipopt
         mv $GITHUB_WORKSPACE/.travis/Makefile $HOME/build/ipopt/src
         make -C $HOME/build/ipopt/src
         mv $HOME/build/ipopt/src/*.mex $HOME/build/ipopt/

.travis.yml

@@ -56,8 +56,8 @@ script:
 # build IPOPT MEX file
 - export PKG_CONFIG_PATH=$TRAVIS_BUILD_DIR/install/lib/pkgconfig
 - mkdir $TRAVIS_BUILD_DIR/build
-- curl -SL https://www.coin-or.org/download/source/Ipopt/Ipopt-${IPOPT_VER}.tgz | tar -xzC $TRAVIS_BUILD_DIR/build
-- mv $TRAVIS_BUILD_DIR/build/Ipopt-${IPOPT_VER}/Ipopt/contrib/MatlabInterface $TRAVIS_BUILD_DIR/build/ipopt
+- curl -SL https://github.com/coin-or/Ipopt/archive/releases/${IPOPT_VER}.tar.gz | tar -xzC $TRAVIS_BUILD_DIR/build
+- mv $TRAVIS_BUILD_DIR/build/Ipopt-releases-${IPOPT_VER}/Ipopt/contrib/MatlabInterface $TRAVIS_BUILD_DIR/build/ipopt
 - mv $TRAVIS_BUILD_DIR/.travis/Makefile $TRAVIS_BUILD_DIR/build/ipopt/src
 - make -C $TRAVIS_BUILD_DIR/build/ipopt/src
 - mv $TRAVIS_BUILD_DIR/build/ipopt/src/*.mex $TRAVIS_BUILD_DIR/build/ipopt/