Improve compile times (PLC-lang#679) (PLC-lang#688)

Added a script which automates the process of creating a `.cargo/config.toml` file to use `lld` as the default linker. Improves linking times by 2x to 4x times.

.devcontainer/Dockerfile

@@ -49,3 +49,6 @@ RUN chmod -R a+rw $CARGO_HOME \
 
 # Switch back to dialog for any ad-hoc use of apt-get
 ENV DEBIAN_FRONTEND=dialog
+
+# Required if we want to use `lld` as the default linker for RuSTy
+RUN ln -sf /usr/bin/ld.lld-$LLVM_VER /usr/bin/ld.lld

.gitignore

@@ -8,3 +8,8 @@
 *.bc
 *.a
 *.elf
+
+# Introduced with issue #679: 
+# We're assuming config.toml to be a local config file for now.
+# This entry has to be removed if a global config file is needed in the near future.
+.cargo/config.toml

book/src/build_and_install.md

@@ -38,5 +38,9 @@ cargo build --release
 
 You can find the binary at `./target/release/rustyc`.
 
+## Improving Compile Times
+By default Rust uses the GNU Linker on Linux which compared to [lld](https://lld.llvm.org/) is slower by a margin of [~2x - 4x](https://llvm.org/devmtg/2016-10/slides/Ueyama-lld.pdf). To improve compile times we can therefore use `lld`. To do so you will need to run the `rusty/scripts/lld.sh` script inside the `rusty` root folder, i.e. by executing `./scripts/lld.sh`. **Note** that the script was only tested on Ubuntu based distributions thus far.
+
+
 ## Installing
 _TODO_

scripts/lld.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env sh
+
+LD_LLD_WITH_VERSION=$(command -v ld.lld-$1)
+LD_LLD_WITHOUT_VERSION=$(command -v ld.lld)
+
+if [ -z $1 ]; then
+    echo "No version specified!"
+    echo "Usage:   $0 <LLD version>"
+    echo "Example: $0 13"
+    exit 1
+fi
+
+# Check if the specified `lld` version is present on the system
+if [ -z $LD_LLD_WITH_VERSION ]; then
+    echo "Could not find ld.lld-$1, make sure lld is installed"
+    exit 1
+fi
+
+# Check if `ld.lld` is present on the system
+if [ -z $LD_LLD_WITHOUT_VERSION ]; then 
+    # Not present, create a symlink into ~/.local/bin
+    mkdir -p $HOME/.local/bin
+    ln -svf $LD_LLD_WITH_VERSION $HOME/.local/bin/ld.lld
+
+    # Append new $PATH to `.bashrc`
+    echo 'export PATH=$HOME/.local/bin:$PATH' >> $HOME/.bashrc
+    echo 'A new $PATH entry has been added to your .bashrc'
+    echo 'For changes to take effect close and reopen your current shell.'
+
+else 
+    # Present, do nothing because we don't want to modifiy system-wide configurations
+    echo "Note: Using already present $LD_LLD_WITHOUT_VERSION binary"
+fi
+
+# Create `config.toml` to make `lld` the default linker for RuSTy
+mkdir -p .cargo
+echo -n '[build]
+rustflags = ["-C", "link-arg=-fuse-ld=lld"]' > .cargo/config.toml
+
+# Makes sure new builds with lld succeed
+cargo clean