fix(dnn/arm): add target os and arch for cross compile

GitOrigin-RevId: a711aceb35ec34284acd38b17b26b6358eae5dc4

toolchains/aarch64-linux-gnu.toolchain.cmake

@@ -4,3 +4,5 @@ set(CMAKE_CXX_COMPILER "aarch64-linux-gnu-g++")
 set(CMAKE_C_FLAGS "-Werror=unused-parameter -Wno-psabi")
 set(CMAKE_CXX_FLAGS "-Werror=unused-parameter -Wno-psabi")
 set(CMAKE_STRIP "aarch64-linux-gnu-strip")
+set(CMAKE_SYSTEM_PROCESSOR aarch64)
+set(CMAKE_SYSTEM_NAME Linux)

toolchains/aarch64-none-linux-gnu.toolchain.cmake

@@ -4,3 +4,5 @@ set(CMAKE_CXX_COMPILER "aarch64-none-linux-gnu-g++")
 set(CMAKE_C_FLAGS "-Werror=unused-parameter -Wno-psabi")
 set(CMAKE_CXX_FLAGS "-Werror=unused-parameter -Wno-psabi")
 set(CMAKE_STRIP "aarch64-none-linux-gnu-strip")
+set(CMAKE_SYSTEM_PROCESSOR aarch64)
+set(CMAKE_SYSTEM_NAME Linux)

toolchains/arm-linux-gnueabi.toolchain.cmake

@@ -4,3 +4,5 @@ set(CMAKE_CXX_COMPILER "arm-linux-gnueabi-g++")
 set(CMAKE_C_FLAGS "-mfloat-abi=softfp -mfpu=neon-vfpv4 -Werror=unused-parameter -Wno-psabi")
 set(CMAKE_CXX_FLAGS "-mfloat-abi=softfp -mfpu=neon-vfpv4 -Werror=unused-parameter -Wno-psabi")
 set(CMAKE_STRIP "arm-linux-gnueabi-strip")
+set(CMAKE_SYSTEM_PROCESSOR armv7)
+set(CMAKE_SYSTEM_NAME Linux)

toolchains/arm-linux-gnueabihf.toolchain.cmake

@@ -4,3 +4,5 @@ set(CMAKE_CXX_COMPILER "arm-linux-gnueabihf-g++")
 set(CMAKE_C_FLAGS "-mfloat-abi=hard -mfpu=neon-vfpv4 -Werror=unused-parameter -Wno-psabi")
 set(CMAKE_CXX_FLAGS "-mfloat-abi=hard -mfpu=neon-vfpv4 -Werror=unused-parameter -Wno-psabi")
 set(CMAKE_STRIP "arm-linux-gnueabihf-strip")
+set(CMAKE_SYSTEM_PROCESSOR armv7)
+set(CMAKE_SYSTEM_NAME Linux)