Rework external dependency fetching to use opendaq_dependency() (#70)

- Replace raw FetchContent_Declare/MakeAvailable with opendaq_dependency() for PcapPlusPlus, npcapsdk, and AsamCmpLib
- Set OPENDAQ_ALWAYS_FETCH_* cache variables to preserve current behavior of always fetching dependencies from source

Author: alexadereyko

external/AsamCmpLib/CMakeLists.txt

@@ -1,11 +1,10 @@
-list(APPEND CMAKE_MESSAGE_CONTEXT AsamCmpLib)
-
+set(OPENDAQ_ALWAYS_FETCH_ASAMCMPLIB ON CACHE BOOL "" FORCE)
 set(ASAM_CMP_LIB_BUILD_EXAMPLE OFF)
 set(ASAM_CMP_LIB_ENABLE_TESTS OFF)
 
-FetchContent_Declare(
-    AsamCmpLib
-    GIT_REPOSITORY https://github.com/openDAQ/ASAM-CMP-Library.git
-    GIT_TAG        v1.0.2-rc
+opendaq_dependency(
+    NAME                AsamCmpLib
+    GIT_REPOSITORY      https://github.com/openDAQ/ASAM-CMP-Library.git 
+    GIT_REF             v1.0.2-rc
+    EXPECT_TARGET       asam_cmp
 )
-FetchContent_MakeAvailable(AsamCmpLib)

external/PcapPlusPlus/CMakeLists.txt

@@ -1,21 +1,19 @@
-list(APPEND CMAKE_MESSAGE_CONTEXT PcapPlusPlus)
-
-
 if(MSVC)
     add_compile_options($<$<COMPILE_LANGUAGE:C,CXX>:/W1>)
     add_compile_options($<$<COMPILE_LANGUAGE:C,CXX>:/wd4068>)
 endif()
 
 if(WIN32)
-    FetchContent_Declare(
-        npcapsdk
-        URL https://npcap.com/dist/npcap-sdk-1.13.zip
+    set(OPENDAQ_ALWAYS_FETCH_NPCAPSDK ON CACHE BOOL "" FORCE)
+    opendaq_dependency(
+        NAME                npcapsdk
+        URL                 https://npcap.com/dist/npcap-sdk-1.13.zip
     )
-    FetchContent_MakeAvailable(npcapsdk)
-    SET(PCAP_ROOT ${npcapsdk_SOURCE_DIR})
+    
+    set(PCAP_ROOT ${npcapsdk_SOURCE_DIR})
+    set(PCAP_LINKS_SOLO ON)
 endif()
 
-
 set(_OLD_CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
 set(_OLD_CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
 
@@ -27,15 +25,13 @@ else()
     set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-implicit-fallthrough -Wno-unused-function")
 endif()
 
-FetchContent_Declare(
-    PcapPlusPlus
-    GIT_REPOSITORY https://github.com/seladb/PcapPlusPlus.git
-    GIT_TAG v25.05
+set(OPENDAQ_ALWAYS_FETCH_PCAPPLUSPLUS ON CACHE BOOL "" FORCE)
+opendaq_dependency(
+    NAME                PcapPlusPlus
+    GIT_REPOSITORY      https://github.com/seladb/PcapPlusPlus.git
+    GIT_REF             v25.05
+    EXPECT_TARGET       Pcap++
 )
-if(WIN32)
-    set(PCAP_LINKS_SOLO ON)
-endif()
-FetchContent_MakeAvailable(PcapPlusPlus)
 
 set(CMAKE_CXX_FLAGS "${_OLD_CMAKE_CXX_FLAGS}")
 set(CMAKE_C_FLAGS "${_OLD_CMAKE_C_FLAGS}")