fix: redirect cdsprpc stub .so out of deliverable output directory

DEVELOPMENT-GUIDE.md

@@ -187,6 +187,29 @@ The library includes several specialized backend implementations:
 - All power metrics measured in milliwatts (mW)
 - Provides average power consumption over sampling period
 
+#### DSP NPU Backend (Linux ARM64)
+- Collects performance metrics from the Qualcomm CDSP/NPU hardware via FastRPC
+- Provides Q6 utilization, Q6 clock, HVX utilization, and HMX utilization metrics
+- Communicates with the DSP using the `sysmonquery` interface over FastRPC
+
+##### Runtime Dependency: `libcdsprpc.so`
+
+The DSP NPU backend requires `libcdsprpc.so` to be present on the target device at runtime. This library is part of the Qualcomm BSP (Board Support Package) and provides the FastRPC transport used to communicate with the CDSP.
+
+> **Note:** `libcdsprpc.so` is **not** built from source — the build system compiles a stub (`cdsprpc_stub.c`) that satisfies the linker at compile time. The real `libcdsprpc.so` must be present on the device at runtime, typically at `/usr/lib/libcdsprpc.so`.
+
+**What happens if `libcdsprpc.so` is missing:**
+
+| Scenario | Behavior |
+|----------|----------|
+| `libcdsprpc.so` absent from device | Dynamic linker fails to load the application — process does not start. No graceful fallback. |
+| `libcdsprpc.so` present, but CDSP inaccessible | `qcom_dsp_init()` returns a non-success error code. `dsp_npu_init()` reports the failure via the message callback at `QC_PERF_MESSAGE_LEVEL_ERROR` and returns `QC_PERF_RETURN_CODE_FAILED`. |
+
+**Recommendation:** Before running an application that uses the DSP NPU backend, verify the library is present on the device:
+```bash
+ls /usr/lib/libcdsprpc.so
+```
+
 ---
 
 ## Adding New Backends

qcperf/backends/qcom-dsp/CMakeLists.txt

@@ -6,14 +6,22 @@ add_library(QcPerfQcomDsp STATIC
 
 add_library(cdsprpc SHARED
     src/cdsprpc_stub.c
-
+
+)
+
+# libcdsprpc.so is a BSP runtime dependency on the target device.
+# This stub exists only to satisfy the linker at build time; it must not
+# be included in the deliverable package.  Redirect it to a separate
+# directory so it cannot be mistaken for a real output artifact.
+set_target_properties(cdsprpc PROPERTIES
+    LIBRARY_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/link-stubs"
 )
 
-target_include_directories(QcPerfQcomDsp PUBLIC 
+target_include_directories(QcPerfQcomDsp PUBLIC
     inc
 )
 
-target_include_directories(cdsprpc PUBLIC 
+target_include_directories(cdsprpc PUBLIC
     inc
 )