Support running make test with PROG_SUFFIX

Signed-off-by: Zhijun <dszhijun@gmail.com>

Author: zhijun42

tests/support/set_executable_path.tcl

@@ -10,6 +10,12 @@ set ::VALKEY_PROG_SUFFIX [expr {
     [info exists ::env(VALKEY_PROG_SUFFIX)] ? $::env(VALKEY_PROG_SUFFIX) : ""
 }]
 
+# Optional program suffix (e.g. `make PROG_SUFFIX=-alt` will create binary valkey-server-alt).
+# Passed from `make test` as environment variable VALKEY_PROG_SUFFIX.
+set ::VALKEY_PROG_SUFFIX [expr {
+    [info exists ::env(VALKEY_PROG_SUFFIX)] ? $::env(VALKEY_PROG_SUFFIX) : ""
+}]
+
 # Helper to build absolute paths
 proc valkey_bin_absolute_path {name} {
     set full_name "${name}${::VALKEY_PROG_SUFFIX}"