Add mold linker build

Allows building the #mold linker, which can then be used in the
cross-toolchain by passing the -fuse-ld=mold to the gcc flags. It is
much faster than ld or gold.

This requires a C++20 compiler and cmake.

Initially implemented by Arnaud, and HC added configure check for cmake.

Outstanding task to validate compiler is C++20 compatible.

Signed-off-by: Arnaud Vrac <avrac@freebox.fr>
Signed-off-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>

2 files changed, 76 insertions, 0 deletions

diff --git a/scripts/build/linker.sh b/scripts/build/linker.sh
new file mode 100644
index 00000000..235d7cf6
--- /dev/null
+++ b/scripts/build/linker.sh
@@ -0,0 +1,38 @@
+# Wrapper to build the standalone linkers
+
+# List all linkers, and parse their scripts
+CT_LINKER_LIST=
+for f in "${CT_LIB_DIR}/scripts/build/linker/"*.sh; do
+    _f="$(basename "${f}" .sh)"
+    _f="${_f#???-}"
+    __f="CT_LINKER_${_f^^}"
+    if [ "${!__f}" = "y" ]; then
+        CT_DoLog DEBUG "Enabling linker '${_f}'"
+        . "${f}"
+        CT_LINKER_LIST="${CT_LINKER_LIST} ${_f}"
+    else
+        CT_DoLog DEBUG "Disabling linker '${_f}'"
+    fi
+done
+
+# Download the linkers
+do_linker_get() {
+    for f in ${CT_LINKER_LIST}; do
+        do_linker_${f}_get
+    done
+}
+
+# Extract and patch the linkers
+do_linker_extract() {
+    for f in ${CT_LINKER_LIST}; do
+        do_linker_${f}_extract
+    done
+}
+
+# Build the linkers
+do_linker() {
+    for f in ${CT_LINKER_LIST}; do
+        do_linker_${f}_build
+    done
+}
+
diff --git a/scripts/build/linker/100-mold.sh b/scripts/build/linker/100-mold.sh
new file mode 100644
index 00000000..710ca969
--- /dev/null
+++ b/scripts/build/linker/100-mold.sh
@@ -0,0 +1,38 @@
+# Build script for the mold linker
+
+do_linker_mold_get() {
+    CT_Fetch MOLD
+}
+
+do_linker_mold_extract() {
+    CT_ExtractPatch MOLD
+}
+
+do_linker_mold_build() {
+    local target_dir="${CT_PREFIX_DIR}/${CT_TARGET}"
+
+    CT_DoStep INFO "Installing mold for host"
+    CT_mkdir_pushd "${CT_BUILD_DIR}/build-mold"
+
+    CT_DoLog EXTRA "Configuring mold for host"
+    CT_DoExecLog CFG                                           \
+    CFLAGS="${CT_CFLAGS_FOR_HOST}"                             \
+    LDFLAGS="${CT_LDFLAGS_FOR_HOST}"                           \
+    cmake "${CT_SRC_DIR}/mold"                                 \
+        -DBUILD_TESTING=OFF                                    \
+        -DMOLD_MOSTLY_STATIC=ON                                \
+        -DCMAKE_BUILD_TYPE=Release
+
+    CT_DoLog EXTRA "Building mold for host"
+    CT_DoExecLog ALL make ${CT_JOBSFLAGS}
+
+    CT_DoLog EXTRA "Installing mold for host"
+    mkdir -p "${target_dir}/bin"
+    cp mold "${target_dir}/bin"
+    ln -s mold "${target_dir}/bin/ld.mold"
+    mkdir -p "${target_dir}/lib/mold"
+    cp mold-wrapper.so "${target_dir}/lib/mold"
+
+    CT_Popd
+    CT_EndStep
+}