[SYCL] Retrieve and print zstd version during configure (#18840)

Here's how the output will look:
```
-- Looking for compress2 - found
-- Found zstd: /iusers/uagarwal/zstd_build/zstd-1.5.6/install/usr/local/lib/libzstd.so
-- Found zstd version 1.5.5.
```

Author: uditagarwal97

llvm/cmake/modules/Findzstd.cmake

@@ -10,6 +10,35 @@
 # zstd::libzstd_shared
 # zstd::libzstd_static
 
+# Function to get zstd version.
+function(get_zstd_version_string zstd_INCLUDE_DIR OUT_VAR)
+
+    # Check if zstd.h file is present. Expectation is that this function will only
+    # be called if zstd is found and the include directory is valid.
+    if(NOT EXISTS "${zstd_INCLUDE_DIR}/zstd.h")
+      message(FATAL_ERROR "zstd.h not found in ${zstd_INCLUDE_DIR}. "
+        "Please set zstd_INCLUDE_DIR to the directory containing zstd.h.")
+    endif()
+
+    # Read the version string from zstd.h.
+    # The version is defined as macros ZSTD_VERSION_MAJOR, ZSTD_VERSION_MINOR,
+    # and ZSTD_VERSION_RELEASE in zstd.h.
+    file(READ "${zstd_INCLUDE_DIR}/zstd.h" content)
+    string(REGEX MATCH "#define[ \t]+ZSTD_VERSION_MAJOR[ \t]+([0-9]+)" _major_match "${content}")
+    string(REGEX MATCH "#define[ \t]+ZSTD_VERSION_MINOR[ \t]+([0-9]+)" _minor_match "${content}")
+    string(REGEX MATCH "#define[ \t]+ZSTD_VERSION_RELEASE[ \t]+([0-9]+)" _patch_match "${content}")
+
+    if(_major_match AND _minor_match AND _patch_match)
+        string(REGEX REPLACE ".*#define[ \t]+ZSTD_VERSION_MAJOR[ \t]+([0-9]+).*" "\\1" _major "${_major_match}")
+        string(REGEX REPLACE ".*#define[ \t]+ZSTD_VERSION_MINOR[ \t]+([0-9]+).*" "\\1" _minor "${_minor_match}")
+        string(REGEX REPLACE ".*#define[ \t]+ZSTD_VERSION_RELEASE[ \t]+([0-9]+).*" "\\1" _patch "${_patch_match}")
+        set(_version "${_major}.${_minor}.${_patch}")
+        set(${OUT_VAR} "${_version}" PARENT_SCOPE)
+    else()
+        set(${OUT_VAR} "" PARENT_SCOPE)
+    endif()
+endfunction()
+
 if(MSVC OR "${CMAKE_CXX_SIMULATE_ID}" STREQUAL "MSVC")
   set(zstd_STATIC_LIBRARY_SUFFIX "_static\\${CMAKE_STATIC_LIBRARY_SUFFIX}$")
 else()
@@ -28,6 +57,12 @@ find_package_handle_standard_args(
     zstd_LIBRARY zstd_INCLUDE_DIR
 )
 
+# Get zstd version.
+if (zstd_FOUND AND zstd_INCLUDE_DIR)
+  get_zstd_version_string("${zstd_INCLUDE_DIR}" zstd_VERSION_STRING)
+  message(STATUS "Found zstd version ${zstd_VERSION_STRING}.")
+endif()
+
 if(zstd_FOUND)
   if(zstd_LIBRARY MATCHES "${zstd_STATIC_LIBRARY_SUFFIX}$")
     set(zstd_STATIC_LIBRARY "${zstd_LIBRARY}")