fxos: add a CMake option to post-process compiler logs

CMakeLists.txt

@@ -6,6 +6,24 @@ add_compile_options(
   -Wall -Wextra -D_GNU_SOURCE -std=c++17 -O2
   -fmacro-prefix-map=${CMAKE_CURRENT_SOURCE_DIR}/=)
 
+# Diagnostic options to clean up output a little bit
+if(FXOS_CLEAN_LOGS)
+  add_compile_options(
+    -fdiagnostics-urls=never -fno-diagnostics-show-caret
+    -fdiagnostics-color=always -fno-diagnostics-show-labels -fno-show-column)
+  # Filter the compiler output through a filter script
+  file(WRITE "${PROJECT_BINARY_DIR}/compiler_filter.sh" "\
+    set -e \n\
+    set -o pipefail \n\
+    \"$@\" |& sed 's#${PROJECT_SOURCE_DIR}/##g' \n\
+  ")
+  file(CHMOD "${PROJECT_BINARY_DIR}/compiler_filter.sh"
+    PERMISSIONS OWNER_READ OWNER_WRITE OWNER_EXECUTE
+                GROUP_READ GROUP_EXECUTE WORLD_READ WORLD_EXECUTE)
+  set_property(GLOBAL PROPERTY RULE_LAUNCH_COMPILE
+    "${PROJECT_BINARY_DIR}/compiler_filter.sh")
+endif()
+
 #---
 # fxos core
 #---

README.md

@@ -33,11 +33,14 @@ requirements.
 * flex (2.6.4)
 * CMake (3.15) and make (eg. 4.2.1)
 
-The only real configure option is the install path. CMake's default is
+There are two configure options:
+
+* `-DCMAKE_INSTALL_PREFIX=<PATH>`: the install path.  CMake's default is
 `/usr/local`; a viable alternative is `$HOME/.local`.
+* `-DFXOS_CLEAN_LOGS=1`: enables basic compiler output filtering to get error messages under control. Tested with GCC.
 
 ```sh
-% cmake -B build # -DCMAKE_INSTALL_PREFIX=$HOME/.local
+% cmake -B build # -DCMAKE_INSTALL_PREFIX=$HOME/.local -DFXOS_CLEAN_LOGS=1
 % make -C build -j$(nproc) install
 ```