Makefile: Add fallback to /opt/rocm home

Makefile

@@ -21,6 +21,9 @@ ifndef ROCM_TARGET
 $(error ERROR: ROCM_TARGET not set. Call make with ROCM string (see https://www.llvm.org/docs/AMDGPUUsage.html#processors), for example: make hip ROCM_TARGET=gfx1030)
 ROCM_TARGET:=
 endif
+else
+$(warning WARNING: Unable to find hipcc in path, fallback to ROCM_HOME /opt/rocm)
+ROCM_HOME:=/opt/rocm
 endif
 
 
@@ -129,7 +132,7 @@ cpuonly: $(BUILD_DIR) env
 hip: $(BUILD_DIR)
 	$(HIPCC) -std=c++14 -c -fPIC --offload-arch=$(ROCM_TARGET) $(HIP_INCLUDE) -o $(BUILD_DIR)/ops.o -DNO_CUBLASLT -DBITS_AND_BYTES_USE_ROCM $(CSRC)/ops.cu
 	$(HIPCC) -std=c++14 -c -fPIC --offload-arch=$(ROCM_TARGET) $(HIP_INCLUDE) -o $(BUILD_DIR)/kernels.o -DNO_CUBLASLT -DBITS_AND_BYTES_USE_ROCM $(CSRC)/kernels.cu
-	# HCC is deprecated, but used by hipBLASlt header. Since blas isn't even used doesn't matter, this is just so that it even compiles
+# HCC is deprecated, but used by hipBLASlt header. Since blas isn't even used doesn't matter, this is just so that it even compiles
 	$(GPP) -std=c++14 -D__HIP_PLATFORM_HCC__ -D__HIP_PLATFORM_AMD__ -DBUILD_CUDA -DBITS_AND_BYTES_USE_ROCM -shared -fPIC $(HIP_INCLUDE) $(BUILD_DIR)/ops.o $(BUILD_DIR)/kernels.o $(FILES_CPP) $(HIP_LIB) -o ./bitsandbytes/libbitsandbytes_hip_nohipblaslt.so
 
 env: