Enforce gcc/g++-11 when building 7.2 FHI through xran

doc/ORAN_FHI7.2_Tutorial.md

@@ -391,6 +391,8 @@ Compile the fronthaul interface library by calling `make` and the option
 environment variables `RTE_SDK` for the path to the source tree of DPDK, and
 `XRAN_DIR` to set the path to the fronthaul library.
 
+**Note**: you need at least gcc-11 and g++-11.
+
 ```bash
 cd ~/phy/fhi_lib/lib
 make clean

radio/fhi_72/CMakeLists.txt

@@ -1,3 +1,10 @@
+# we need at least gcc-11 to build xran, so let's enforce it here
+# (because xran might not check it, and we have control here)
+if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS 11.0
+   OR CMAKE_C_COMPILER_VERSION VERSION_LESS 11.0)
+ message(FATAL_ERROR "you need to have at least gcc/g++-11 to use 7.2 FHI through xran")
+endif()
+
 # use env var PKG_CONFIG_PATH to override paths to libdpdk.pc
 pkg_check_modules(dpdk REQUIRED libdpdk)
 pkg_check_modules(numa REQUIRED numa)