bootstrap: Add option to use system libuv during bootstrap

Support bootstrapping on older systems where our bundled
version libuv does not compile (.e.g Centos5, see #19086 and #19311).
Add a `--bootstrap-system-libuv` option to use the system-provided
libuv even for the bootstrap binary itself.

bootstrap

@@ -632,6 +632,8 @@ Configuration:
   --system-libuv          use system-installed libuv library
   --no-system-libuv       use cmake-provided libuv library (default)
 
+  --bootstrap-system-libuv use system-installed libuv library for boostrap
+
   --qt-gui                build the Qt-based GUI (requires Qt >= 4.2)
   --no-qt-gui             do not build the Qt-based GUI (default)
   --qt-qmake=<qmake>      use <qmake> as the qmake executable to find Qt
@@ -854,6 +856,7 @@ cmake_verbose=
 cmake_parallel_make=
 cmake_ccache_enabled=
 cmake_prefix_dir="${cmake_default_prefix}"
+bootstrap_system_libuv=
 while test $# != 0; do
   case "$1" in
   --prefix=*) dir=`cmake_arg "$1"`
@@ -873,6 +876,7 @@ while test $# != 0; do
   --no-system-bzip2|--no-system-curl|--no-system-expat|--no-system-jsoncpp|--no-system-libarchive|--no-system-librhash|--no-system-zlib|--no-system-liblzma|--no-system-zstd|--no-system-libuv)
     lib=`cmake_arg "$1" "--no-system-"`
     cmake_bootstrap_system_libs="${cmake_bootstrap_system_libs} -DCMAKE_USE_SYSTEM_LIBRARY_`cmake_toupper $lib`=0" ;;
+  --bootstrap-system-libuv) bootstrap_system_libuv="1" ;;
   --qt-gui) cmake_bootstrap_qt_gui="1" ;;
   --no-qt-gui) cmake_bootstrap_qt_gui="0" ;;
   --qt-qmake=*) cmake_bootstrap_qt_qmake=`cmake_arg "$1"` ;;
@@ -1488,9 +1492,11 @@ objs=""
 for a in ${CMAKE_CXX_SOURCES} ${CMAKE_C_SOURCES} ${CMAKE_STD_CXX_SOURCES} ${LexerParser_CXX_SOURCES} ${LexerParser_C_SOURCES} ${KWSYS_CXX_SOURCES} ${KWSYS_C_SOURCES}; do
   objs="${objs} ${a}.o"
 done
-for a in ${LIBUV_C_SOURCES}; do
-  objs="${objs} uv-`cmake_obj ${a}`"
-done
+if test "x${bootstrap_system_libuv}" = "x"; then
+  for a in ${LIBUV_C_SOURCES}; do
+    objs="${objs} uv-`cmake_obj ${a}`"
+  done
+fi
 
 libs=""
 
@@ -1528,14 +1534,20 @@ else
       ;;
   esac
 fi
-uv_c_flags="${uv_c_flags} `cmake_escape "-I${cmake_source_dir}/Utilities/cmlibuv/include"`"
-if ${cmake_system_mingw}; then
-  uv_c_flags="${uv_c_flags} `cmake_escape "-I${cmake_source_dir}/Utilities/cmlibuv/src/win"`"
+if test "x${bootstrap_system_libuv}" = "x"; then
+  uv_c_flags="${uv_c_flags} `cmake_escape "-I${cmake_source_dir}/Utilities/cmlibuv/include"`"
+  if ${cmake_system_mingw}; then
+    uv_c_flags="${uv_c_flags} `cmake_escape "-I${cmake_source_dir}/Utilities/cmlibuv/src/win"`"
+  else
+    uv_c_flags="${uv_c_flags} `cmake_escape "-I${cmake_source_dir}/Utilities/cmlibuv/src/unix"`"
+  fi
+  uv_c_flags="${uv_c_flags} `cmake_escape "-I${cmake_source_dir}/Utilities/cmlibuv/src"`"
 else
-  uv_c_flags="${uv_c_flags} `cmake_escape "-I${cmake_source_dir}/Utilities/cmlibuv/src/unix"`"
+  if test `which pkg-config`; then
+    uv_c_flags="${uv_c_flags} `pkg-config --cflags libuv`"
+  fi
+  libs="${libs} -luv"
 fi
-uv_c_flags="${uv_c_flags} `cmake_escape "-I${cmake_source_dir}/Utilities/cmlibuv/src"`"
-
 if test "x${cmake_ansi_cxx_flags}" != "x"; then
   cmake_cxx_flags="${cmake_ansi_cxx_flags} ${cmake_cxx_flags}"
 fi
@@ -1617,11 +1629,13 @@ for a in ${KWSYS_CXX_SOURCES}; do
   echo "${a}.o : ${src} ${dep}" >> "${cmake_bootstrap_dir}/Makefile"
   echo "	${cmake_cxx_compiler} ${cmake_cxx_flags} -DKWSYS_NAMESPACE=cmsys ${src_flags} -c ${src} -o ${a}.o" >> "${cmake_bootstrap_dir}/Makefile"
 done
-for a in ${LIBUV_C_SOURCES}; do
-  src=`cmake_escape "${cmake_source_dir}/Utilities/cmlibuv/${a}"`
-  echo "uv-`cmake_obj ${a}` : ${src} ${dep}" >> "${cmake_bootstrap_dir}/Makefile"
-  echo "	${cmake_c_compiler} ${cmake_c_flags} ${uv_c_flags} -c ${src} -o uv-`cmake_obj ${a}`" >> "${cmake_bootstrap_dir}/Makefile"
-done
+if test "x${bootstrap_system_libuv}" = "x"; then
+  for a in ${LIBUV_C_SOURCES}; do
+    src=`cmake_escape "${cmake_source_dir}/Utilities/cmlibuv/${a}"`
+    echo "uv-`cmake_obj ${a}` : ${src} ${dep}" >> "${cmake_bootstrap_dir}/Makefile"
+    echo "	${cmake_c_compiler} ${cmake_c_flags} ${uv_c_flags} -c ${src} -o uv-`cmake_obj ${a}`" >> "${cmake_bootstrap_dir}/Makefile"
+  done
+fi
 echo '
 rebuild_cache:
 	cd "${cmake_binary_dir}" && "${cmake_source_dir}/bootstrap"