build: "undo" the coverage compiling options added to abseil

we are not interseted in the code coverage of abseil library, so no need
to apply the compiling options enabling the coverage instrumentation
when building the abseil library.

moreover, since the path of the file passed to `-fprofile-list` is a relative
path. when building with coverage enabled, the build fails when building
abseil, like:

```
 /usr/lib64/ccache/clang++  -I/jenkins/workspace/scylla-master/scylla-ci/scylla/abseil -std=c++20 -I/jenkins/workspace/scylla-master/scylla-ci/scylla/seastar/include -I/jenkins/workspace/scylla-master/scylla-ci/scylla/build/debug/seastar/gen/include -U_FORTIFY_SOURCE -Werror=unused-result -fstack-clash-protection -fsanitize=address -fsanitize=undefined -fno-sanitize=vptr -DSEASTAR_API_LEVEL=7 -DSEASTAR_BUILD_SHARED_LIBS -DSEASTAR_SSTRING -DSEASTAR_LOGGER_COMPILE_TIME_FMT -DSEASTAR_SCHEDULING_GROUPS_COUNT=16 -DSEASTAR_DEBUG -DSEASTAR_DEFAULT_ALLOCATOR -DSEASTAR_SHUFFLE_TASK_QUEUE -DSEASTAR_DEBUG_SHARED_PTR -DSEASTAR_DEBUG_PROMISE -DSEASTAR_LOGGER_TYPE_STDOUT -DSEASTAR_TYPE_ERASE_MORE -DBOOST_NO_CXX98_FUNCTION_BASE -DFMT_SHARED -I/usr/include/p11-kit-1 -fprofile-instr-generate -fcoverage-mapping -fprofile-list=./coverage_sources.list -std=gnu++20 -Wall -Wextra -Wcast-qual -Wconversion -Wfloat-overflow-conversion -Wfloat-zero-conversion -Wfor-loop-analysis -Wformat-security -Wgnu-redeclared-enum -Winfinite-recursion -Winvalid-constexpr -Wliteral-conversion -Wmissing-declarations -Woverlength-strings -Wpointer-arith -Wself-assign -Wshadow-all -Wshorten-64-to-32 -Wsign-conversion -Wstring-conversion -Wtautological-overlap-compare -Wtautological-unsigned-zero-compare -Wundef -Wuninitialized -Wunreachable-code -Wunused-comparison -Wunused-local-typedefs -Wunused-result -Wvla -Wwrite-strings -Wno-float-conversion -Wno-implicit-float-conversion -Wno-implicit-int-float-conversion -Wno-unknown-warning-option -DNOMINMAX -MD -MT absl/strings/CMakeFiles/strings.dir/str_cat.cc.o -MF absl/strings/CMakeFiles/strings.dir/str_cat.cc.o.d -o absl/strings/CMakeFiles/strings.dir/str_cat.cc.o -c /jenkins/workspace/scylla-master/scylla-ci/scylla/abseil/absl/strings/str_cat.cc
clang-16: error: no such file or directory: './coverage_sources.list'`
```

in this change, we just remove the compiling options enabling the
coverage instrumentation from the cflags when building abseil.

Fixes #18686
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>

Closes scylladb/scylladb#18748

configure.py

@@ -1762,6 +1762,12 @@ def configure_abseil(build_dir, mode, mode_config):
     abseil_build_dir = os.path.join(build_dir, mode, 'abseil')
 
     abseil_cflags = seastar_cflags + ' ' + modes[mode]['cxx_ld_flags']
+    # We want to "undo" coverage for abseil if we have it enabled, as we are not
+    # interested in the coverage of the abseil library. these flags were previously
+    # added to cxx_ld_flags
+    if args.coverage:
+        for flag in COVERAGE_INST_FLAGS:
+            abseil_cflags = abseil_cflags.replace(f' {flag}', '')
     cmake_mode = mode_config['cmake_build_type']
     abseil_cmake_args = [
         '-DCMAKE_BUILD_TYPE={}'.format(cmake_mode),