build(openwrt): use single toolchain location

Previously, the toolchain was being built in the CMAKE_BINARY_DIR. However, libpcap uses the command, `check_include_file()`, which creates a new CMake project in a temporary folder to test C/C++ features. This causes the OpenWRT SDK to be constantly downloaded multiple times, taking a lot of time. Instead, I've changed the OpenWRT toolchain file to download and extract the SDK next to the toolchain file. This should let the SDK be cached.
nqminds · May 24, 2022 · 49e3000 · 49e3000
1 parent c527013
commit 49e3000
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diff --git a/CMakeModules/CMakeToolchains/.gitignore b/CMakeModules/CMakeToolchains/.gitignore
@@ -0,0 +1,2 @@
+# ignore toolchains downloaded by FetchContent
+/build
diff --git a/CMakeModules/CMakeToolchains/openwrt-mvebu-cortexa9.cmake b/CMakeModules/CMakeToolchains/openwrt-mvebu-cortexa9.cmake
@@ -16,6 +16,9 @@ if(NOT DEFINED openwrt_toolchain_location)
         URL https://downloads.openwrt.org/releases/19.07.10/targets/mvebu/cortexa9/openwrt-sdk-19.07.10-mvebu-cortexa9_gcc-7.5.0_musl_eabi.Linux-x86_64.tar.xz
         # sha256 from https://downloads.openwrt.org/releases/19.07.10/targets/mvebu/cortexa9/sha256sums
         URL_HASH SHA256=17941f42e26d3c54a836f9897e78abaafcf66e5f0b28ffd8956378aa69c3a4d9
+        # Make sure that that the toolchain location is indepent from CMAKE_BINARY_DIR/CMAKE_SOURCE_DIR
+        # otherwise `check_include_file()` commands will redownload these files slowly
+        PREFIX "${CMAKE_CURRENT_LIST_DIR}/build/openwrt_sdk_mvebu_cortexa9"
     )
     FetchContent_Populate(openwrt_sdk_mvebu_cortexa9)
     set(