Merge #20359: depends: Various config.site.in improvements and linting

46756a6987 depends: Fix PYTHONPATH setting in config.site.in (Carl Dong)
618cbd2c1a lint: Also lint files with shellcheck directive (Carl Dong)
6c7e8f067d depends: Allow relative CONFIG_SITE path env var (Carl Dong)

Pull request description:

  This changeset:

  1. Allows the `CONFIG_SITE` env var to be a relative path rather than requiring an absolute one
  2. Enables linting of the `config.site.in` file with `shellcheck` in our linting scripts
  3. Sets the `PYTHONPATH` var sensibly in `config.site.in`

  Please see commit messages for more details

ACKs for top commit:
  laanwj:
    ACK 46756a6987

Tree-SHA512: 744089b9f6e5604e56466d9a3e64563f9183a70f7e300ac9ae6248f0f17c0b53fe28a2c41d43c5ffe5da825f53c2ca21f21aacba0579442da3056fb0c4b81454

depends/config.site.in

@@ -1,4 +1,14 @@
-depends_prefix="`dirname ${ac_site_file}`/.."
+# shellcheck shell=sh disable=SC2034 # Many variables set will be used in
+                                     # ./configure but shellcheck doesn't know
+                                     # that, hence: disable=SC2034
+
+true  # Dummy command because shellcheck treats all directives before first
+      # command as file-wide, and we only want to disable for one line.
+      #
+      # See: https://github.com/koalaman/shellcheck/wiki/Directive
+
+# shellcheck disable=SC2154
+depends_prefix="$(cd "$(dirname ${ac_site_file})/.." && pwd)"
 
 cross_compiling=maybe
 host_alias=@HOST@
@@ -50,7 +60,7 @@ if test x@host_os@ = xdarwin; then
 fi
 
 PATH=$depends_prefix/native/bin:$PATH
-PKG_CONFIG="`which pkg-config` --static"
+PKG_CONFIG="$(which pkg-config) --static"
 
 # These two need to remain exported because pkg-config does not see them
 # otherwise. That means they must be unexported at the end of configure.ac to
@@ -69,7 +79,7 @@ fi
 if test -n "@CXX@" -a -z "${CXX}"; then
   CXX="@CXX@"
 fi
-PYTHONPATH=$depends_prefix/native/lib/python3/dist-packages:$PYTHONPATH
+PYTHONPATH="${depends_prefix}/native/lib/python3/dist-packages${PYTHONPATH:+${PATH_SEPARATOR}}${PYTHONPATH}"
 
 if test -n "@AR@"; then
   AR=@AR@

test/lint/lint-shell.sh

@@ -36,7 +36,8 @@ fi
 
 SHELLCHECK_CMD=(shellcheck --external-sources --check-sourced)
 EXCLUDE="--exclude=$(IFS=','; echo "${disabled[*]}")"
-if ! "${SHELLCHECK_CMD[@]}" "$EXCLUDE" $(git ls-files -- '*.sh' | grep -vE 'src/(leveldb|secp256k1|univalue)/'); then
+SOURCED_FILES=$(git ls-files | xargs gawk '/^# shellcheck shell=/ {print FILENAME} {nextfile}')  # Check shellcheck directive used for sourced files
+if ! "${SHELLCHECK_CMD[@]}" "$EXCLUDE" $SOURCED_FILES $(git ls-files -- '*.sh' | grep -vE 'src/(leveldb|secp256k1|univalue)/'); then
     EXIT_CODE=1
 fi