Revert "[pkg/vm] Handle cross compilation in the precompiler2 sc..."

Revert changes to precompiler2 and dart_precompiled_runtime.

Reason for revert: Golem is broken because host_arch helper does not handle aarch64 as a possibility (which is what we get from uname on these machines).

Reverted changes: /q/submissionid:404600

Change-Id: I88cbaba2a369d6deeca0866ef28dc220ca4bf4d6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/405641
Bot-Commit: Rubber Stamper <[email protected]>
Reviewed-by: Alexander Markov <[email protected]>
Commit-Queue: Slava Egorov <[email protected]>

Author: mraleph

pkg/vm/tool/precompiler2

@@ -15,7 +15,7 @@
 set -e
 
 function follow_links() {
-  local file="$1"
+  file="$1"
   while [ -h "$file" ]; do
     # On Mac OS, readlink -f doesn't work.
     file="$(readlink "$file")"
@@ -31,8 +31,6 @@ CUR_DIR="$(cd "${PROG_NAME%/*}" ; pwd -P)"
 
 SDK_DIR="$CUR_DIR/../../.."
 
-. "$CUR_DIR/shared_functions.sh"
-
 OPTIONS=()
 GEN_KERNEL_OPTIONS=()
 PACKAGES=
@@ -100,36 +98,18 @@ else
   OUT_DIR="$SDK_DIR/out"
 fi
 
-HOST_ARCH="$(host_arch)"
+HOST_ARCH="X64"
+if [[ `uname -m` == 'arm64' ]]; then
+  HOST_ARCH="ARM64"
+fi
 
 export DART_CONFIGURATION=${DART_CONFIGURATION:-Release$HOST_ARCH}
-TARGET_ARCH="$(parse_target_arch "$DART_CONFIGURATION")"
 BUILD_DIR="$OUT_DIR/$DART_CONFIGURATION"
-if [ ! -d "$BUILD_DIR" ]; then
-  echo "$BUILD_DIR is not a directory"
-  exit 1
-fi
-
-function find_dart {
-  local tools_dart="${SDK_DIR}/tools/sdks/dart-sdk/bin/dart"
-  if [ -f "$tools_dart" ]; then
-    echo "$tools_dart"
-  else
-    local host_dart=""
-    if [[ "$HOST_ARCH" == "$TARGET_ARCH" ]]; then
-      host_dart="$BUILD_DIR/dart"
-    else
-      host_dart="$OUT_DIR/Release$HOST_ARCH/dart"
-    fi
-    if [ ! -f "$host_dart" ]; then
-      echo "Cannot find dart at either $tools_dart or $host_dart"
-      exit 1
-    fi
-    echo "$host_dart"
-  fi
-}
 
-DART="$(find_dart)"
+DART="${SDK_DIR}/tools/sdks/dart-sdk/bin/dart"
+if [ ! -f "$DART" ]; then
+  DART="$BUILD_DIR/dart"
+fi
 
 function gen_kernel() {
   if [[ "$DART_GN_ARGS" == *"precompile_tools=true"* ]]; then
@@ -149,29 +129,10 @@ gen_kernel --platform "${BUILD_DIR}/vm_platform_strong.dill"                   \
      -o "$SNAPSHOT_FILE.dill"                                                  \
      "$SOURCE_FILE"
 
-GEN_SNAPSHOT="gen_snapshot"
-# If the target architecture differs from the host architecture, use
-# gen_snapshot for the host architecture for cross compilation, which is
-# denoted by an X between the build mode and the architecture name,
-# e.g., ReleaseXARM64 on X64.
-if [[ ( "$DART_CONFIGURATION" =~ (Debug|Release|Product)X[^6] ) && \
-      ( "$HOST_ARCH" != "$TARGET_ARCH" ) ]]; then
-  case "$HOST_ARCH" in
-    "X64")
-    GEN_SNAPSHOT="clang_x64/${GEN_SNAPSHOT}"
-    ;;
-    "ARM64")
-    GEN_SNAPSHOT="clang_arm64/${GEN_SNAPSHOT}"
-    ;;
-    *)
-    echo "Unexpected host architecture $HOST_ARCH for cross compilation"
-    exit 1
-    ;;
-  esac
-fi
+
 
 # Step 2: Generate snapshot from the Kernel binary.
-${BUILD_DIR}/${GEN_SNAPSHOT}                                                   \
+"$BUILD_DIR"/gen_snapshot                                                      \
      ${GEN_SNAPSHOT_FLAGS}                                                     \
      "$GEN_SNAPSHOT_OPTION"                                                    \
      "$GEN_SNAPSHOT_FILENAME"                                                  \