cmake: allow providing SYCL_DIR (#699)

allow providing SYCL_DIR

Author: fschlimb

cmake/modules/FindSyclRuntime.cmake

@@ -27,27 +27,33 @@
 
 include(FindPackageHandleStandardArgs)
 
-if(NOT DEFINED ENV{CMPLR_ROOT})
+if(NOT DEFINED ENV{CMPLR_ROOT} AND NOT DEFINED ENV{SYCL_DIR})
     message(WARNING "Please make sure to install Intel DPC++ Compiler and run setvars.(sh/bat)")
     message(WARNING "You can download standalone Intel DPC++ Compiler from https://www.intel.com/content/www/us/en/developer/articles/tool/oneapi-standalone-components.html#compilers")
+    message(Warning "Alternatively, you can set environment SYCL_DIR to the install dir of SYCL")
 else()
-    get_filename_component(ONEAPI_VER "$ENV{CMPLR_ROOT}" NAME)
-    # Adding more precise detection for SYCL runtime folder name
-    if (ONEAPI_VER)
-        string(REGEX MATCH "[0-9]+.[0-9]+[.0-9]*" VER_NUMBER ${ONEAPI_VER})
+    if(DEFINED ENV{SYCL_DIR})
+        set(SyclRuntime_ROOT "$ENV{SYCL_DIR}")
     else()
-        set(VER_NUMBER FALSE)
-    endif()
+        get_filename_component(ONEAPI_VER "$ENV{CMPLR_ROOT}" NAME)
+        # Adding more precise detection for SYCL runtime folder name
+        if (ONEAPI_VER)
+            string(REGEX MATCH "[0-9]+.[0-9]+[.0-9]*" VER_NUMBER ${ONEAPI_VER})
+        else()
+            set(VER_NUMBER FALSE)
+        endif()
 
-    if(VER_NUMBER AND ONEAPI_VER VERSION_LESS 2024.0)
-        if(LINUX OR (${CMAKE_SYSTEM_NAME} MATCHES "Linux"))
-            set(SyclRuntime_ROOT "$ENV{CMPLR_ROOT}/linux")
-        elseif(WIN32)
-            set(SyclRuntime_ROOT "$ENV{CMPLR_ROOT}/windows")
+        if(VER_NUMBER AND ONEAPI_VER VERSION_LESS 2024.0)
+            if(LINUX OR (${CMAKE_SYSTEM_NAME} MATCHES "Linux"))
+                set(SyclRuntime_ROOT "$ENV{CMPLR_ROOT}/linux")
+            elseif(WIN32)
+                set(SyclRuntime_ROOT "$ENV{CMPLR_ROOT}/windows")
+            endif()
+        else()
+            set(SyclRuntime_ROOT "$ENV{CMPLR_ROOT}")
         endif()
-    else()
-        set(SyclRuntime_ROOT "$ENV{CMPLR_ROOT}")
     endif()
+
     list(APPEND SyclRuntime_INCLUDE_DIRS "${SyclRuntime_ROOT}/include")
     list(APPEND SyclRuntime_INCLUDE_DIRS "${SyclRuntime_ROOT}/include/sycl")