[BUILD] Fix CMake logic to detect DISABLE_NIC_EXEC (#195)

CMakeLists.txt

@@ -126,8 +126,12 @@ if(HSA_LIBRARY AND HSA_INCLUDE_DIR)
 endif()
 
 ## Check for infiniband verbs support
-if(DEFINED ENV{ENABLE_NIC_EXEC} OR DEFINED ENABLE_NIC_EXEC)
-  message(STATUS "For CMake builds, NIC executor also requires explicit opt-in by setting CMake flag -DENABLE_NIC_EXEC=1 or environment flag ENABLE_NIC_EXEC=1")
+if(DEFINED ENV{DISABLE_NIC_EXEC} AND "$ENV{DISABLE_NIC_EXEC}" STREQUAL "1")
+  message(STATUS "Disabling NIC Executor support as env. flag DISABLE_NIC_EXEC was enabled")
+elseif(NOT ENABLE_NIC_EXEC)
+  message(STATUS "For CMake builds, NIC executor so requires explicit opt-in by setting CMake flag -DENABLE_NIC_EXEC=1")
+  message(STATUS "Disabling NIC Executor support")
+else()
   find_library(IBVERBS_LIBRARY ibverbs)
   find_path(IBVERBS_INCLUDE_DIR infiniband/verbs.h)
   if(IBVERBS_LIBRARY AND IBVERBS_INCLUDE_DIR)
@@ -143,9 +147,6 @@ if(DEFINED ENV{ENABLE_NIC_EXEC} OR DEFINED ENABLE_NIC_EXEC)
     endif()
     message(WARNING "Building without NIC executor support. To use the TransferBench RDMA executor, check if your system has NICs, the NIC drivers are installed, and libibverbs-dev is installed")
   endif()
-else()
-  message(STATUS "Disabling NIC Executor support")
-  message(WARNING "For CMake builds, NIC executor requires explicit opt-in by setting ENABLE_NIC_EXEC=1")
 endif()
 
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY .)