GN: Add Windows support to bootstrap.py

tools/gn/bootstrap/build_vs.ninja.template

Index: tools/gn/bootstrap/build_vs.ninja.template
diff --git a/tools/gn/bootstrap/build_vs.ninja.template b/tools/gn/bootstrap/build_vs.ninja.template
new file mode 100644
index 0000000000000000000000000000000000000000..6e98575b22afd1f504fa0b39dba75ff2edabf7ad
--- /dev/null
+++ b/tools/gn/bootstrap/build_vs.ninja.template
@@ -0,0 +1,25 @@
+rule cc
+  command = $cc /nologo /showIncludes /FC @${out}.rsp /c ${in} /Fo${out}
+  description = CC ${out}
+  rspfile = ${out}.rsp
+  rspfile_content = ${defines} ${includes} ${cflags} ${cflags_c}
+  deps = msvc
+
+rule cxx
+  command = $cxx /nologo /showIncludes /FC @${out}.rsp /c ${in} /Fo${out}
+  description = CXX ${out}
+  rspfile = ${out}.rsp
+  rspfile_content = ${defines} ${includes} ${cflags} ${cflags_cc}
+  deps = msvc
+
+rule alink_thin
+  command = $ar /nologo /ignore:4221 /OUT:${out} @${out}.rsp
+  description = LIB ${out}
+  rspfile = ${out}.rsp
+  rspfile_content = ${in_newline}
+
+rule link
+  command = $ld /nologo /OUT:${out} /PDB:${out}.pdb @${out}.rsp
+  description = LINK ${out}
+  rspfile = ${out}.rsp
+  rspfile_content = ${in_newline} ${libs} ${solibs} ${ldflags}