Add missing ci scripts

ci/scripts/build.linux.script.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+
+set -x
+
+# Create and enter build directory.
+rootdir=`pwd`
+mkdir -p ${EIGEN_CI_BUILDDIR}
+cd ${EIGEN_CI_BUILDDIR}
+
+# Configure build.
+cmake -G Ninja                                                   \
+  -DCMAKE_CXX_COMPILER=${EIGEN_CI_CXX_COMPILER}                  \
+  -DCMAKE_C_COMPILER=${EIGEN_CI_C_COMPILER}                      \
+  -DCMAKE_CXX_COMPILER_TARGET=${EIGEN_CI_CXX_COMPILER_TARGET}    \
+  ${EIGEN_CI_ADDITIONAL_ARGS} ${rootdir}
+
+target=""
+if [[ ${EIGEN_CI_BUILD_TARGET} ]]; then
+  target="--target ${EIGEN_CI_BUILD_TARGET}"
+fi
+
+# Builds (particularly gcc) sometimes get killed, potentially when running
+# out of resources.  In that case, keep trying to build the remaining
+# targets (k0), then try to build again with a single thread (j1) to minimize
+# resource use.
+cmake --build . ${target} -- -k0 || cmake --build . ${target} -- -k0 -j1
+
+# Return to root directory.
+cd ${rootdir}
+
+set +x