build: add option EMIL_FETCH_ECHO_COMPILERS to avoid building the com…

…pilers even on host (#718)

* build: add option EMIL_FETCH_ECHO_COMPILERS to avoid building the compilers even on host

* Fetch echo compilers by default

CMakeLists.txt

@@ -72,8 +72,10 @@ endif()
 # options.
 if (EMIL_STANDALONE AND EMIL_HOST_BUILD)
     set(EMIL_DEFAULTOPT On)
+    set(EMIL_DEFAULTOPT_INVERTED Off)
 else()
     set(EMIL_DEFAULTOPT Off)
+    set(EMIL_DEFAULTOPT_INVERTED On)
 endif()
 
 # When building EmIL by itself do not exclude any targets from all
@@ -90,7 +92,13 @@ option(EMIL_ENABLE_FUZZING "Enable building the fuzzing targets" Off)
 option(EMIL_ENABLE_DOCKER_TOOLS "Enable shift-left tools (e.g. linters, formatters) that are run using Docker" On)
 option(EMIL_GENERATE_PACKAGE_CONFIG "Enable generation of package configuration and install files" ${EMIL_HOST_BUILD})
 option(EMIL_ENABLE_TRACING "Enable Tracing" On)
-option(EMIL_BUILD_ECHO_COMPILERS "Build and install the Protobuf ECHO compilers" ${EMIL_DEFAULTOPT})
+option(EMIL_FETCH_ECHO_COMPILERS "Fetch the Protobuf ECHO compilers from GitHub" ${EMIL_DEFAULTOPT_INVERTED})
+if (NOT EMIL_FETCH_ECHO_COMPILERS)
+    set(EMIL_DEFAULTOPT_BUILD_ECHO_COMPILERS ${EMIL_DEFAULTOPT})
+else()
+    set(EMIL_DEFAULTOPT_BUILD_ECHO_COMPILERS Off)
+endif()
+option(EMIL_BUILD_ECHO_COMPILERS "Build and install the Protobuf ECHO compilers" ${EMIL_DEFAULTOPT_BUILD_ECHO_COMPILERS})
 
 # Enable or disable optional features.
 option(EMIL_INCLUDE_MBEDTLS "Include MbedTLS as part of EmIL" On)

protobuf/echo/protocol_buffer_echo.cmake

@@ -7,7 +7,7 @@ function(emil_fetch_echo_plugins)
     #
     # (See: https://cmake.org/cmake/help/latest/module/FetchContent.html#commands)
 
-    if (EMIL_HOST_BUILD AND NOT CMAKE_CROSSCOMPILING)
+    if (EMIL_HOST_BUILD AND NOT CMAKE_CROSSCOMPILING AND NOT EMIL_FETCH_ECHO_COMPILERS)
         # In a host build where we are not cross-compiling we use the built echo plug-ins
         return()
     endif()

protobuf/protoc_echo_plugin/CMakeLists.txt

@@ -1,4 +1,4 @@
-if (EMIL_HOST_BUILD)
+if (EMIL_HOST_BUILD AND NOT EMIL_FETCH_ECHO_COMPILERS)
     add_library(protobuf.protoc_echo_plugin_lib ${EMIL_EXCLUDE_FROM_ALL} STATIC)
 
     target_compile_definitions(protobuf.protoc_echo_plugin_lib PRIVATE

protobuf/protoc_echo_plugin/test/CMakeLists.txt

@@ -1,5 +1,11 @@
+if (EMIL_FETCH_ECHO_COMPILERS)
+    set(NOT_EMIL_FETCH_ECHO_COMPILERS false)
+else()
+    set(NOT_EMIL_FETCH_ECHO_COMPILERS true)
+endif()
+
 add_executable(protobuf.protoc_echo_plugin_test)
-emil_build_for(protobuf.protoc_echo_plugin_test BOOL EMIL_BUILD_TESTS)
+emil_build_for(protobuf.protoc_echo_plugin_test BOOL EMIL_BUILD_TESTS PREREQUISITE_BOOL NOT_EMIL_FETCH_ECHO_COMPILERS)
 emil_add_test(protobuf.protoc_echo_plugin_test)
 
 protocol_buffer_echo_cpp(protobuf.protoc_echo_plugin_test ../../echo/test/TestMessages.proto)

protobuf/protoc_echo_plugin_csharp/CMakeLists.txt

@@ -1,4 +1,4 @@
-if (EMIL_HOST_BUILD AND NOT CMAKE_CROSSCOMPILING)
+if (EMIL_HOST_BUILD AND NOT CMAKE_CROSSCOMPILING AND NOT EMIL_FETCH_ECHO_COMPILERS)
     add_executable(protobuf.protoc_echo_plugin_csharp)
     emil_build_for(protobuf.protoc_echo_plugin_csharp BOOL EMIL_BUILD_ECHO_COMPILERS)
     emil_install(protobuf.protoc_echo_plugin_csharp EXPORT emilProtobufTargets DESTINATION bin)

protobuf/protoc_echo_plugin_java/CMakeLists.txt

@@ -1,4 +1,4 @@
-if (EMIL_HOST_BUILD AND NOT CMAKE_CROSSCOMPILING)
+if (EMIL_HOST_BUILD AND NOT CMAKE_CROSSCOMPILING AND NOT EMIL_FETCH_ECHO_COMPILERS)
     add_executable(protobuf.protoc_echo_plugin_java)
     emil_build_for(protobuf.protoc_echo_plugin_java BOOL EMIL_BUILD_ECHO_COMPILERS)
     emil_install(protobuf.protoc_echo_plugin_java EXPORT emilProtobufTargets DESTINATION bin)