Reorganize the contents of $BUILD_TMP

In preparation for building the toolchain on the host, check for
existence of a stamp file before executing a build step and create
such file after the build step succeedes.

Define the subdirectories of $BUILD_TMP to be used by its sub-processes
in the main build-all.sh script.

Improve the diagnostic messages.

Author: atrosinenko

scripts/build-all.sh

@@ -1,13 +1,15 @@
 #!/usr/bin/env sh
-set -xe
+set -e
 
 # This script invokes all other build-*.sh scripts.
 # Inside the container, it is called by build-in-docker.sh.
 # FIXME: Add another entry point script to perform build directly on host.
 
+set -x
 cd "$(dirname "$0")"
 . "$REPO_ROOT/config"
 . ./global-vars
+set +x
 
 write_clang_config_files() {
   cat > "$INSTALL_DIR/bin/aarch64-unknown-linux-pauthtest.cfg" <<EOF
@@ -20,19 +22,63 @@ $EXTRA_FLAGS_MUSL
 EOF
 }
 
+# Usage: try_build <stamp-prefix> <command line...>
+# Note:  CROSS_TARGET is added to the stamp file name.
+#
+# Try performing the build step:
+# * skip this step if the stamp file already exists
+# * create the stamp file if the build step succeeded
+# * print an error to the user if the build step failed
+#
+# The primary goal of this function is to improve usability of restarting
+# partially successful builds performed on the host. Note that no directories
+# are removed in case of an error to minimize the amount of "rm -rf" calls
+# performed on the host and to simplify the debugging of build errors.
+try_build() {
+  local stamp_prefix="$1"
+  shift 1
+
+  local build_dir="${BUILD_TMP}/${stamp_prefix}-${CROSS_TARGET}"
+
+  local stamp_file_name="${build_dir}.stamp"
+  if [ -f "$stamp_file_name" ]; then
+    echo "Stamp found, skipping '$*'."
+    return
+  fi
+
+  if [ -d "$build_dir" ]; then
+    echo "Incomplete build directory is found at $build_dir." 1>&2
+    exit 1
+  fi
+
+  # Try performing the build step.
+  # On error, print a message to the user instead on exiting due to 'set -e'.
+
+  export BUILD_DIR="$build_dir" # Used by called subprocess.
+  echo "Executing: $*"
+  if "$@"; then
+    touch "$stamp_file_name"
+  else
+    echo "Execution of '$stamp_prefix' step for '$CROSS_TARGET' failed." 1>&2
+    echo "Please remove incomplete build at '$BUILD_DIR' before restarting the build." 1>&2
+    exit 1
+  fi
+}
+
 build_target_libs() {
   export CROSS_TARGET
   export TARGET_PREFIX="$INSTALL_DIR/$CROSS_TARGET/usr"
-  ./create-symlinks.sh
-  ./build-linux-header.sh
-  LIBC_STARTFILE_STAGE=1 ./build-musl.sh
-  COMPILER_RT_BUILD=builtins ./build-compiler-rt.sh
-  ./build-musl.sh
-  ./build-runtimes.sh
-  COMPILER_RT_BUILD=full ./build-compiler-rt.sh
+  echo "Building runtime libs in $TARGET_PREFIX..."
+  try_build symlinks      ./create-symlinks.sh
+  try_build linux-headers ./build-linux-header.sh
+  LIBC_STARTFILE_STAGE=1     try_build musl-startfiles      ./build-musl.sh
+  COMPILER_RT_BUILD=builtins try_build compiler-rt-builtins ./build-compiler-rt.sh
+  try_build musl-full ./build-musl.sh
+  try_build runtimes  ./build-runtimes.sh
+  COMPILER_RT_BUILD=full     try_build compiler-rt-full ./build-compiler-rt.sh
 }
 
-./build-llvm.sh
+CROSS_TARGET="all" try_build llvm ./build-llvm.sh
 
 write_clang_config_files
 CROSS_TARGET="aarch64-linux-pauthtest" build_target_libs

scripts/build-compiler-rt.sh

@@ -4,8 +4,6 @@ cd "$(dirname "$0")"
 . "$REPO_ROOT/config"
 . ./global-vars
 
-BUILD_DIR="${BUILD_TMP}/compiler-rt-${COMPILER_RT_BUILD}-${CROSS_TARGET}"
-
 COMPILER_RT_INSTALL_PREFIX="$("$INSTALL_DIR/bin/clang" --print-resource-dir)"
 
 # Assertion: COMPILER_RT_INSTALL_PREFIX should be under INSTALL_DIR.

scripts/build-linux-header.sh

@@ -8,8 +8,6 @@ KERNEL_ARCH=arm64
 TARBALL_BASENAME="linux-$LINUX_KERNEL_VERSION.tar.xz"
 TARBALL_PATH="$SRC_DIR/$TARBALL_BASENAME"
 
-BUILD_DIR="$BUILD_TMP/linux-headers-${CROSS_TARGET}"
-
 mkdir "$BUILD_DIR"
 tar -axf "$TARBALL_PATH" -C "$BUILD_DIR" --strip 1
 mkdir "$BUILD_DIR/build-$KERNEL_ARCH"

scripts/build-llvm.sh

@@ -4,8 +4,6 @@ cd "$(dirname "$0")"
 . "$REPO_ROOT/config"
 . ./global-vars
 
-BUILD_DIR="$BUILD_TMP/llvm"
-
 cmake \
   -S "$LLVM_SOURCE_DIR/llvm" \
   -B "$BUILD_DIR" \

scripts/build-musl.sh

@@ -4,8 +4,6 @@ cd "$(dirname "$0")"
 . "$REPO_ROOT/config"
 . ./global-vars
 
-BUILD_DIR="${BUILD_TMP}/musl-${CROSS_TARGET}"
-[ ! -n "$LIBC_STARTFILE_STAGE" ] && BUILD_DIR="$BUILD_DIR-full"
 mkdir "$BUILD_DIR"
 cd "$BUILD_DIR"
 

scripts/build-runtimes.sh

@@ -4,8 +4,6 @@ cd "$(dirname "$0")"
 . "$REPO_ROOT/config"
 . ./global-vars
 
-BUILD_DIR="$BUILD_TMP/runtimes-${CROSS_TARGET}"
-
 if [ -d "$TARGET_PREFIX/include/c++" ]; then
   echo "ERROR: The destination directory already exists: $TARGET_PREFIX/include/c++" 1>&2
   exit 1