chore(build): fix issues with build_standalone.sh (#15105)

## Description

This PR updates `build_standalone.sh` to fix certain issues or usability
shortcomings I've encountered with it.

* Pass `-gdwarf-4` because the `valgrind` version we have on workspaces
doesn't support DWARF 5
* Report an error early if `clang`/`gcc` isn't available (e.g. not
installed in the workspace) instead of letting CMake fail later with a
less clear error message
* Add `-v|--valgrind` in the help message (which was already supported,
but not documented)
* Validate that there are exactly three arguments

Author: KowalskiThomas

ddtrace/internal/datadog/profiling/build_standalone.sh

@@ -94,7 +94,7 @@ compiler_args["cppcheck"]="-DDO_CPPCHECK=ON"
 compiler_args["infer"]="-DDO_INFER=ON"
 compiler_args["clangtidy"]="-DDO_CLANGTIDY=ON"
 compiler_args["clangtidy_cmd"]="-DCLANGTIDY_CMD=${CLANGTIDY_CMD}"
-compiler_args["valgrind"]="-DDO_VALGRIND=ON"
+compiler_args["valgrind"]="-DDO_VALGRIND=ON -DCMAKE_CXX_FLAGS=-gdwarf-4 -DCMAKE_C_FLAGS=-gdwarf-4"
 
 ctest_args=()
 
@@ -126,6 +126,12 @@ set_cc() {
 
 # Helper functions for finding the compiler(s)
 set_clang() {
+  # Check that clang is available (required for most build modes)
+  if [[ -z "$highest_clang" ]] || [[ -z "$highest_clangxx" ]]; then
+    echo "Error: clang/clang++ not found. This build mode requires clang."
+    exit 1
+  fi
+
   if [ -z "${CC:-}" ]; then
     export CC=$highest_clang
   fi
@@ -139,6 +145,12 @@ set_clang() {
 }
 
 set_gcc() {
+  # Check that gcc/g++ is available (required for most build modes)
+  if [[ -z "$highest_gcc" ]] || [[ -z "$highest_gxx" ]]; then
+    echo "Error: gcc/g++ not found. This build mode requires gcc."
+    exit 1
+  fi
+
   # Only set CC or CXX if they're not set
   if [ -z "${CC:-}" ]; then
     export CC=$highest_gcc
@@ -197,7 +209,8 @@ print_help() {
   echo "  -C  --cppcheck    Clang + " ${compiler_args["cppcheck"]}
   echo "  -I  --infer       Clang + " ${compiler_args["infer"]}
   echo "  -T  --clangtidy   Clang + " ${compiler_args["clangtidy"]}
-  echo "  -f, --fanalyze    GCC + " ${compiler_args["fanalyzer"]}
+  echo "  -f, --fanalyze    GCC   + " ${compiler_args["fanalyzer"]}
+  echo "  -v, --valgrind    Clang + Valgrind + " ${compiler_args["valgrind"]}
   echo "  -c, --clang       Clang (alone)"
   echo "  -g, --gcc         GCC (alone)"
   echo "  --                Don't do anything special"
@@ -207,11 +220,9 @@ print_help() {
   echo "  Release"
   echo "  RelWithDebInfo"
   echo ""
-  echo "(any possible others, depending on what cmake supports for"
-  echo "BUILD_TYPE out of the box)"
+  echo "(any possible others, depending on what cmake supports for BUILD_TYPE out of the box)"
   echo ""
   echo "Targets:"
-  echo "  all"
   echo "  all_test (default)"
   echo "  stack_v2 (also builds dd_wrapper)"
   echo "  stack_v2_test (also builds dd_wrapper_test)"
@@ -268,7 +279,7 @@ add_compiler_args() {
       cmake_args+=(${compiler_args["memory"]})
       set_clang
       ;;
-    --valgrind)
+    -v|--valgrind)
       cmake_args+=(${compiler_args["valgrind"]})
       ctest_args+="-T memcheck"
       set_clang
@@ -370,6 +381,12 @@ if [ $# -eq 0 ]; then
   exit 1
 fi
 
+if [ $# -ne 3 ]; then
+  echo "Error: Expected exactly 3 arguments"
+  print_help
+  exit 1
+fi
+
 add_compiler_args "$1"
 add_build_mode "$2"
 add_target "$3"