tests/assert-install.sh: Always to enforce correct installation

Also in this change:

- now we call ln(1) in the "install" target without using the -r
  "relative" flag, as it isn't POSIX;
- add `+` as a prefix to the "assert-tests" command, so we tell sub-make
  calls to also run things in parallel.  In this case, the
  "make DESTDIR=... install" calls;
- use the implicit `index.js` entrypoint and do away completly with
  `package.json`;
- change from `import` to `require` as Node.js ESM modules don't support
  `$NODE_PATH`[0]: "NODE_PATH is not part of resolving import
  specifiers. Please use symlinks if this behavior is desired." 🤦;

The parallel sub-make behaviour isn't available in current specification
of make (POSIX issue 7) but is included in the upcoming[1] version 8:

> If a rule invokes a sub-make either via the MAKE macro or via a
> command line that begins with '+', the sub-make is the same
> implementation as the make that invoked the sub-make, and the −j
> option is passed to the sub-make via the MAKEFLAGS environment
> variable with the same maxjobs value and is not overridden by a
> maxjobs value from another source (even if it has the same value), the
> sub-make shall use the same token pool as its invoking make rather
> than create a new token pool.

[0]: https://nodejs.org/api/esm.html#no-node_path
[1]: https://www.opengroup.org/austin/restricted/202x-d3/202x_d3.pdf

2 files changed, 34 insertions, 1 deletions

diff --git a/tools/lib.sh b/tools/lib.sh
new file mode 100644
index 0000000..9d183f9
--- /dev/null
+++ b/tools/lib.sh
@@ -0,0 +1,33 @@
+#!/bin/sh
+
+assert_arg() {
+	if [ -z "$1" ]; then
+		printf 'Missing %s.\n\n' "$2" >&2
+		cat <<-'EOF'
+			usage >&2
+			exit 2
+		EOF
+	fi
+}
+
+uuid() {
+        od -xN20 /dev/urandom |
+                head -n1 |
+                awk '{OFS="-"; print $2$3,$4,$5,$6,$7$8$9}'
+}
+
+tmpname() {
+        echo "${TMPDIR:-/tmp}/uuid-tmpname with spaces.$(uuid)"
+}
+
+mkstemp() {
+	name="$(tmpname)"
+	touch "$name"
+	echo "$name"
+}
+
+mkdtemp() {
+        name="$(tmpname)"
+	mkdir "$name"
+        echo "$name"
+}
diff --git a/tools/manpages.sh b/tools/manpages.sh
index 959b1c2..755ff77 100755
--- a/tools/manpages.sh
+++ b/tools/manpages.sh
@@ -1,7 +1,7 @@
 #!/bin/sh
 set -eu
 
-. tests/lib.sh
+. tools/lib.sh
 
 
 usage() {