[v0.30] Allow users to select backend from build script

Before we had AMD support, CMakeLists.txt tried to enable all backends
by default. Now that we have AMD support, that does not make that much
sense so instead it will only enable the backend specified by the user
(with the -DENABLE_XXX_BACKEND flags)

Then, before AMD support, the build.sh script was useful to just
invoke cmake and let it figure out the backends, but the script was
a bit useless after the mentioned change in the CMakeLists.txt.

Therefore, this commit allow users to specify an argument, like:

./build.sh cuda

To specify what backend/s to enable, without the need to manually
configure the build with the -DENABLE_XXX_BACKEND flag. Note that
multiple backends are also allowed, like:

./build.sh intel,hsa

Would enable both Intel and HSA backends (which could make sense for
example in a system with Intel iGPU an an AMD dGPU).

build.sh

@@ -1,5 +1,24 @@
 #!/bin/bash
 
+print_help() {
+  cat << EOF
+Usage: $0 <backends> [build_type]
+
+  <backends>    MANDATORY. Comma-separated list of 
+                backends to enable.
+                Valid options: hsa, intel, cuda
+                Example: hsa,cuda
+
+  [build_type]  OPTIONAL. Build type. Valid options:
+                debug, release (default: release)
+
+Examples:
+  $0 hsa,intel debug
+  $0 cuda
+  $0 hsa,intel,cuda release
+EOF
+}
+
 # gpufetch build script
 set -e
 
@@ -7,19 +26,79 @@ rm -rf build/ gpufetch
 mkdir build/
 cd build/
 
-if [ "$1" == "debug" ]
+if [ "$1" == "--help" ]
 then
-  BUILD_TYPE="Debug"
-else
-  BUILD_TYPE="Release"
+  echo "gpufetch build script"
+  echo
+  print_help
+  exit 0
 fi
 
+if [[ $# -lt 1 ]]; then
+  echo "ERROR: At least one backend must be specified."
+  echo
+  print_help
+  exit 1
+fi
+
+# Determine if last argument is build type
+LAST_ARG="${!#}"
+if [[ "$LAST_ARG" == "debug" || "$LAST_ARG" == "release" ]]; then
+  BUILD_TYPE="$LAST_ARG"
+  BACKEND_ARG="${1}"
+else
+  BUILD_TYPE="release"
+  BACKEND_ARG="${1}"
+fi
+
+# Split comma-separated backends into an array
+IFS=',' read -r -a BACKENDS <<< "$BACKEND_ARG"
+
+# Validate build type 
+if [[ "$BUILD_TYPE" != "debug" && "$BUILD_TYPE" != "release" ]]
+then
+  echo "Error: Invalid build type '$BUILD_TYPE'."
+  echo "Valid options are: debug, release"
+  exit 1
+fi
+
+# From lower to upper case
+CMAKE_FLAGS="-DCMAKE_BUILD_TYPE=${BUILD_TYPE^}"
+
+# Validate backends
+VALID_BACKENDS=("hsa" "intel" "cuda")
+
+for BACKEND in "${BACKENDS[@]}"; do
+  case "$BACKEND" in
+    hsa)
+      CMAKE_FLAGS+=" -DENABLE_HSA_BACKEND=ON"
+      ;;
+    intel)
+      CMAKE_FLAGS+=" -DENABLE_INTEL_BACKEND=ON"
+      ;;
+    cuda)
+      CMAKE_FLAGS+=" -DENABLE_CUDA_BACKEND=ON"
+      ;;
+    *)
+      echo "ERROR: Invalid backend '$BACKEND'."
+      echo "Valid options: ${VALID_BACKENDS[*]}"
+      exit 1
+      ;;
+  esac
+done
+
+# You can also manually specify the compilation flags.
+# If you need to, just run the cmake command directly
+# instead of using this script.
+#
+# Here you will find some help:
+#
 # In case you have CUDA installed but it is not detected,
 # - set CMAKE_CUDA_COMPILER to your nvcc binary:
 # - set CMAKE_CUDA_COMPILER_TOOLKIT_ROOT to the CUDA root dir
 # for example:
 # cmake -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DCMAKE_CUDA_COMPILER=/usr/local/cuda/bin/nvcc -DCMAKE_CUDA_COMPILER_TOOLKIT_ROOT=/usr/local/cuda/ ..
-
+#
 # In case you want to explicitely disable a backend, you can:
 # Disable CUDA backend:
 # cmake -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DENABLE_CUDA_BACKEND=OFF ..
@@ -28,7 +107,9 @@ fi
 # Disable Intel backend:
 # cmake -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DENABLE_INTEL_BACKEND=OFF ..
 
-cmake -DCMAKE_BUILD_TYPE=$BUILD_TYPE ..
+echo "$0: Running cmake $CMAKE_FLAGS"
+echo 
+cmake $CMAKE_FLAGS ..
 
 os=$(uname)
 if [ "$os" == 'Linux' ]; then