Compile Modsecurity v3.x for WASM architecture

Using emscripten (emconfigure and emmake) I am working on compiling the library libmodsecurity for WebAssembly.
Referring to this issue and this solution, the main problem that I'm facing is that I am including paths to system headers (-I/usr/include -I/usr/include/libxml2). Could anyone help me to figure out how to modify the MakeFile to avoid these inclusions?
The command that I should change is:

/home/user/Tesi/extensions/manualBuild/emsdk/upstream/bin/clang++ -target wasm32-unknown-emscripten -DEMSCRIPTEN -fignore-exceptions -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr -D__EMSCRIPTEN_major__=2 -D__EMSCRIPTEN_minor__=0 -D__EMSCRIPTEN_tiny__=25 -D_LIBCPP_ABI_VERSION=2 -Dunix -D__unix -D__unix__ -Werror=implicit-function-declaration -Xclang -iwithsysroot/include/SDL --sysroot=/home/user/Tesi/extensions/manualBuild/emsdk/upstream/emscripten/cache/sysroot -Xclang -iwithsysroot/include/compat -DHAVE_CONFIG_H -I. -std=c++11 -I.. -g -I../others -fPIC -O3 -I../headers -DWITH_CURL_SSLVERSION_TLSv1_2 -DWITH_CURL -DWITH_GEOIP -I/usr/include -I/usr/include/libxml2 -DWITH_LIBXML2 -g -O2 -MT parser/libmodsecurity_la-seclang-parser.lo -MD -MP -MF parser/.deps/libmodsecurity_la-seclang-parser.Tpo -c -fPIC -DPIC parser/seclang-parser.cc -o parser/.libs/libmodsecurity_la-seclang-parser.o

Action performed are just:
./build.sh
emconfigure ./configure
emmake make
Resulting in this error:

/bin/bash ../libtool  --tag=CXX   --mode=compile /home/user/Tesi/extensions/manualBuild/emsdk/upstream/emscripten/em++ -DHAVE_CONFIG_H -I.  -std=c++11 -I.. -g -I../others -fPIC -O3 -I../headers -DWITH_CURL_SSLVERSION_TLSv1_2 -DWITH_CURL -DWITH_GEOIP -I/usr/include          -I/usr/include/libxml2 -DWITH_LIBXML2   -g -O2 -MT parser/libmodsecurity_la-seclang-parser.lo -MD -MP -MF parser/.deps/libmodsecurity_la-seclang-parser.Tpo -c -o parser/libmodsecurity_la-seclang-parser.lo `test -f 'parser/seclang-parser.cc' || echo './'`parser/seclang-parser.cc
libtool: compile:  /home/user/Tesi/extensions/manualBuild/emsdk/upstream/emscripten/em++ -DHAVE_CONFIG_H -I. -std=c++11 -I.. -g -I../others -fPIC -O3 -I../headers -DWITH_CURL_SSLVERSION_TLSv1_2 -DWITH_CURL -DWITH_GEOIP -I/usr/include -I/usr/include/libxml2 -DWITH_LIBXML2 -g -O2 -MT parser/libmodsecurity_la-seclang-parser.lo -MD -MP -MF parser/.deps/libmodsecurity_la-seclang-parser.Tpo -c parser/seclang-parser.cc  -fPIC -DPIC -o parser/.libs/libmodsecurity_la-seclang-parser.o
In file included from parser/seclang-parser.cc:41:
In file included from seclang-parser.yy:11:
In file included from /home/user/Tesi/extensions/manualBuild/emsdk/upstream/emscripten/cache/sysroot/include/c++/v1/string:511:
In file included from /home/user/Tesi/extensions/manualBuild/emsdk/upstream/emscripten/cache/sysroot/include/c++/v1/string_view:179:
In file included from /home/user/Tesi/extensions/manualBuild/emsdk/upstream/emscripten/cache/sysroot/include/c++/v1/__string:57:
In file included from /home/user/Tesi/extensions/manualBuild/emsdk/upstream/emscripten/cache/sysroot/include/c++/v1/algorithm:651:
In file included from /home/user/Tesi/extensions/manualBuild/emsdk/upstream/emscripten/cache/sysroot/include/c++/v1/cstring:60:
/usr/include/string.h:26:10: fatal error: 'bits/libc-header-start.h' file not found
#include <bits/libc-header-start.h>
         ^~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.
em++: error: '/home/user/Tesi/extensions/manualBuild/emsdk/upstream/bin/clang++ -target wasm32-unknown-emscripten -DEMSCRIPTEN -fignore-exceptions -mllvm -combiner-global-alias-analysis=false -mllvm -enable-emscripten-sjlj -mllvm -disable-lsr -D__EMSCRIPTEN_major__=2 -D__EMSCRIPTEN_minor__=0 -D__EMSCRIPTEN_tiny__=25 -D_LIBCPP_ABI_VERSION=2 -Dunix -D__unix -D__unix__ -Werror=implicit-function-declaration -Xclang -iwithsysroot/include/SDL --sysroot=/home/user/Tesi/extensions/manualBuild/emsdk/upstream/emscripten/cache/sysroot -Xclang -iwithsysroot/include/compat -DHAVE_CONFIG_H -I. -std=c++11 -I.. -g -I../others -fPIC -O3 -I../headers -DWITH_CURL_SSLVERSION_TLSv1_2 -DWITH_CURL -DWITH_GEOIP -I/usr/include -I/usr/include/libxml2 -DWITH_LIBXML2 -g -O2 -MT parser/libmodsecurity_la-seclang-parser.lo -MD -MP -MF parser/.deps/libmodsecurity_la-seclang-parser.Tpo -c -fPIC -DPIC parser/seclang-parser.cc -o parser/.libs/libmodsecurity_la-seclang-parser.o' failed (returned 1)
make[3]: *** [Makefile:2072: parser/libmodsecurity_la-seclang-parser.lo] Error 1
make[3]: Leaving directory '/home/user/Tesi/extensions/manualBuild/ModSecurity/src'
make[2]: *** [Makefile:3479: all-recursive] Error 1
make[2]: Leaving directory '/home/user/Tesi/extensions/manualBuild/ModSecurity/src'
make[1]: *** [Makefile:1224: all] Error 2
make[1]: Leaving directory '/home/user/Tesi/extensions/manualBuild/ModSecurity/src'
make: *** [Makefile:1035: all-recursive] Error 1
emmake: error: 'make' failed (returned 2)

Thanks for any help about the generation and the possibility to change this building phase