Add --compiler flag and GNU compiler support

Flags for release and debug configurations for the GNU compiler were
taken from build.ksh (CABLE-POP_TRENDY branch).

CMakeLists.txt

@@ -27,6 +27,18 @@ if(CMAKE_Fortran_COMPILER_ID MATCHES "Intel")
     )
 endif()
 
+set(CABLE_GNU_Fortran_FLAGS -cpp -ffree-form -ffixed-line-length-132)
+set(CABLE_GNU_Fortran_FLAGS_DEBUG -O -g -pedantic-errors -Wall -W -Wno-maybe-uninitialized -fbacktrace -ffpe-trap=zero,overflow,underflow -finit-real=nan)
+set(CABLE_GNU_Fortran_FLAGS_RELEASE -O3 -Wno-aggressive-loop-optimizations)
+if(CMAKE_Fortran_COMPILER_ID MATCHES "GNU")
+    set(
+        CABLE_Fortran_FLAGS
+        ${CABLE_GNU_Fortran_FLAGS}
+        "$<$<CONFIG:Release>:${CABLE_GNU_Fortran_FLAGS_RELEASE}>"
+        "$<$<CONFIG:Debug>:${CABLE_GNU_Fortran_FLAGS_DEBUG}>"
+    )
+endif()
+
 add_library(
     cable_common_objlib
     OBJECT

build.bash

@@ -14,6 +14,8 @@ options below will be passed to CMake when generating the build system.
 Options:
       --clean   Delete build directory before invoking CMake.
       --mpi     Compile MPI executable.
+      --compiler <compiler>
+                Specify the compiler to use.
   -j <jobs>     Specify the number of parallel jobs in the compilation. By
                 default this value is set to $nproc_default.
   -h, --help    Show this screen.
@@ -43,6 +45,10 @@ while [ $# -gt 0 ]; do
             mpi=1
             cmake_args+=(-DCABLE_MPI="ON")
             ;;
+        --compiler)
+            compiler=$2
+            shift
+            ;;
         -j)
             CMAKE_BUILD_PARALLEL_LEVEL=$2
             shift
@@ -59,14 +65,24 @@ while [ $# -gt 0 ]; do
 done
 
 if hostname -f | grep gadi.nci.org.au > /dev/null; then
+    : "${compiler:=Intel}"
+
     . /etc/bashrc
     module purge
     module add cmake/3.24.2
-    module add intel-compiler/2019.5.281
     module add netcdf/4.6.3
+    case ${compiler} in
+        Intel)
+            module add intel-compiler/2019.5.281
+            ;;
+        GNU)
+            module add gcc/13.2.0
+            ;;
+    esac
+
     # This is required so that the netcdf-fortran library is discoverable by
     # pkg-config:
-    prepend_path PKG_CONFIG_PATH "${NETCDF_BASE}/lib/Intel/pkgconfig"
+    prepend_path PKG_CONFIG_PATH "${NETCDF_BASE}/lib/${compiler}/pkgconfig"
 
     if [[ -n $mpi ]]; then
         module add intel-mpi/2019.5.281
@@ -75,7 +91,7 @@ if hostname -f | grep gadi.nci.org.au > /dev/null; then
     if module is-loaded openmpi; then
         # This is required so that the openmpi MPI libraries are discoverable
         # via CMake's `find_package` mechanism:
-        prepend_path CMAKE_PREFIX_PATH "${OPENMPI_BASE}/include/Intel"
+        prepend_path CMAKE_PREFIX_PATH "${OPENMPI_BASE}/include/${compiler}"
     fi
 fi