Generate CFG_FILENAME_EXTRA from the version

The code takes a prefix of the MD5 hash of the version string.

Since the hash command differs across GNU and BSD platforms, we scan for
the right one in the configure script.

Closes #25007

configure

@@ -709,6 +709,20 @@ else
     probe_need CFG_GIT     git
 fi
 
+# Use `md5sum` on GNU platforms, or `md5 -q` on BSD
+probe CFG_MD5              md5
+probe CFG_MD5SUM           md5sum
+if [ -n "$CFG_MD5" ]
+then
+    CFG_HASH_COMMAND="$CFG_MD5 -q | head -c 8"
+elif [ -n "$CFG_MD5SUM" ]
+then
+    CFG_HASH_COMMAND="$CFG_MD5SUM | head -c 8"
+else
+    err 'could not find one of: md5 md5sum'
+fi
+putvar CFG_HASH_COMMAND
+
 probe CFG_CLANG            clang++
 probe CFG_CCACHE           ccache
 probe CFG_GCC              gcc

mk/main.mk

@@ -20,7 +20,9 @@ CFG_RELEASE_NUM=1.1.0
 # versions (section 9)
 CFG_PRERELEASE_VERSION=.1
 
-CFG_FILENAME_EXTRA=4e7c5e5c
+# Append a version-dependent hash to each library, so we can install different
+# versions in the same place
+CFG_FILENAME_EXTRA=$(shell echo -n $(CFG_RELEASE) | $(CFG_HASH_COMMAND))
 
 ifeq ($(CFG_RELEASE_CHANNEL),stable)
 # This is the normal semver version string, e.g. "0.12.0", "0.12.0-nightly"