cmake: add -g to existing RUSTFLAGS if required

Makes it possible to use the sanitizers again.

Note that this requires RUSTFLAGS to be set when running CMake, and will not be
updated when running the build system if the environment variable changes.

CMakeLists.txt

@@ -102,7 +102,6 @@ add_custom_command(
   OUTPUT ${rust_target_dir}/${rust_profile}/libfish.rlib
   COMMAND ${CMAKE_COMMAND} -E env
       ${VARS_FOR_CARGO}
-      $<$<CONFIG:Debug,RelWithDebInfo>:RUSTFLAGS=-g>
     ${Rust_CARGO} ARGS
       build --lib
       $<$<CONFIG:Release,RelWithDebInfo>:--release>
@@ -122,7 +121,6 @@ function(FISH_LINK_DEPS_AND_SIGN target)
     OUTPUT ${rust_target_dir}/${rust_profile}/${target}
     COMMAND ${CMAKE_COMMAND} -E env
       ${VARS_FOR_CARGO}
-      $<$<CONFIG:Debug,RelWithDebInfo>:RUSTFLAGS=-g>
     ${Rust_CARGO} ARGS build --bin ${target}
       $<$<CONFIG:Release,RelWithDebInfo>:--release>
       --target ${Rust_CARGO_TARGET}

cmake/Rust.cmake

@@ -19,6 +19,8 @@ else()
 endif()
 
 set(rust_profile $<IF:$<CONFIG:Debug>,debug,release>)
+set(rust_debugflags "$<$<CONFIG:Debug,RelWithDebInfo>:-g>")
+
 
 # Temporary hack to propogate CMake flags/options to build.rs. We need to get CMake to evaluate the
 # truthiness of the strings if they are set.
@@ -56,4 +58,5 @@ set(VARS_FOR_CARGO
     "CARGO_TARGET_DIR=${FISH_RUST_BUILD_DIR}"
     "CARGO_BUILD_RUSTC=${RUSTC_EXECUTABLE}"
     "${FISH_PCRE2_BUILDFLAG}"
+    "RUSTFLAGS=$ENV{RUSTFLAGS} ${rust_debugflags}"
 )