guix: Move DISTSRC determination to guix-build.sh

contrib/guix/guix-build.sh

@@ -64,6 +64,50 @@ else
     GIT_COMMIT=$(git rev-parse --short=12 HEAD)
 fi
 
+################
+# Check 4: Make sure that build directories do no exist
+################
+
+# Default to building for all supported HOSTs (overridable by environment)
+export HOSTS="${HOSTS:-x86_64-linux-gnu arm-linux-gnueabihf aarch64-linux-gnu riscv64-linux-gnu
+                       x86_64-w64-mingw32}"
+
+DISTSRC_BASE="${DISTSRC_BASE:-${PWD}}"
+
+# Usage: distsrc_for_host HOST
+#
+#   HOST: The current platform triple we're building for
+#
+distsrc_for_host() {
+    echo "${DISTSRC_BASE}/distsrc-${GIT_COMMIT}-${1}"
+}
+
+# Accumulate a list of build directories that already exist...
+hosts_distsrc_exists=""
+for host in $HOSTS; do
+    if [ -e "$(distsrc_for_host "$host")" ]; then
+        hosts_distsrc_exists+=" ${host}"
+    fi
+done
+
+if [ -n "$hosts_distsrc_exists" ]; then
+# ...so that we can print them out nicely in an error message
+cat << EOF
+ERR: Build directories for this commit already exist for the following platform
+     triples you're attempting to build, probably because of previous builds.
+     Please remove, or otherwise deal with them prior to starting another build.
+
+     Aborting...
+
+EOF
+for host in $hosts_distsrc_exists; do
+    echo "     ${host} '$(distsrc_for_host "$host")'"
+done
+exit 1
+else
+    mkdir -p "$DISTSRC_BASE"
+fi
+
 #########
 # Setup #
 #########
@@ -116,9 +160,9 @@ and untracked files and directories will be wiped, allowing you to start anew.
 EOF
 }
 
-# Deterministically build Bitcoin Core for HOSTs (overridable by environment)
+# Deterministically build Bitcoin Core
 # shellcheck disable=SC2153
-for host in ${HOSTS=x86_64-linux-gnu arm-linux-gnueabihf aarch64-linux-gnu riscv64-linux-gnu x86_64-w64-mingw32}; do
+for host in $HOSTS; do
 
     # Display proper warning when the user interrupts the build
     trap 'int_trap ${host}' INT
@@ -187,12 +231,13 @@ for host in ${HOSTS=x86_64-linux-gnu arm-linux-gnueabihf aarch64-linux-gnu riscv
         #    Please read the README.md in the same directory as this file for
         #    more information.
         #
-        # shellcheck disable=SC2086
+        # shellcheck disable=SC2086,SC2031
         time-machine environment --manifest="${PWD}/contrib/guix/manifest.scm" \
                                  --container \
                                  --pure \
                                  --no-cwd \
                                  --share="$PWD"=/bitcoin \
+                                 --share="$DISTSRC_BASE"=/distsrc-base \
                                  --share="$OUTDIR"=/outdir \
                                  --expose="$(git rev-parse --git-common-dir)" \
                                  ${SOURCES_PATH:+--share="$SOURCES_PATH"} \
@@ -204,6 +249,7 @@ for host in ${HOSTS=x86_64-linux-gnu arm-linux-gnueabihf aarch64-linux-gnu riscv
                                         SOURCE_DATE_EPOCH="${SOURCE_DATE_EPOCH:?unable to determine value}" \
                                         ${V:+V=1} \
                                         ${SOURCES_PATH:+SOURCES_PATH="$SOURCES_PATH"} \
+                                        DISTSRC="$(DISTSRC_BASE=/distsrc-base && distsrc_for_host "$HOST")" \
                                         OUTDIR=/outdir \
                                       bash -c "cd /bitcoin && bash contrib/guix/libexec/build.sh"
     )

contrib/guix/libexec/build.sh

@@ -23,15 +23,6 @@ echo "At most ${MAX_JOBS:?not set} jobs will run at once..."
 # $HOSTs after successfully building.
 BASEPREFIX="${PWD}/depends"
 
-# Setup the directory where our Bitcoin Core build for HOST will occur
-DISTSRC="${DISTSRC:-${PWD}/distsrc-${HOST}}"
-if [ -e "$DISTSRC" ]; then
-    echo "DISTSRC directory '${DISTSRC}' exists, probably because of previous builds... Aborting..."
-    exit 1
-else
-    mkdir -p "$DISTSRC"
-fi
-
 # Given a package name and an output name, return the path of that output in our
 # current guix environment
 store_path() {
@@ -185,6 +176,7 @@ esac
 
 # Make $HOST-specific native binaries from depends available in $PATH
 export PATH="${BASEPREFIX}/${HOST}/native/bin:${PATH}"
+mkdir -p "$DISTSRC"
 (
     cd "$DISTSRC"