ninja windows: Add build.ninja variable to turn on dep_database
ninja windows: Add build.ninja variable to turn on dep_database

Part of upstreaming, adding top-level ninja flag indicating that 'depfile'
entry is a key for the dep_database.

R=thakis@chromium.org
Review URL: https://chromiumcodereview.appspot.com/10834116

git-svn-id: e7e1075985beda50ea81ac4472467b4f6e91fc78@1447 78cadc50-ecff-11dd-a971-7dbc132099af

bulldy80/gyp_unofficial,omasanori/gyp,chromium/gyp,Chilledheart/gyp,ttyangf/gyp,mkrautz/gyp-libmumble,yjhjstz/gyp,sanyaade-teachings/gyp,trafi/gyp,azunite/gyp,ryfx/gyp,enkripsi/gyp,ttyangf/gyp,svn2github/gyp,cchamberlain/gyp,bdarnell/gyp,mapbox/gyp,LazyCodingCat/gyp,adblockplus/gyp,springmeyer/gyp,Jack-Q/GYP-copy,brson/gyp,ttyangf/pdfium_gyp,amoikevin/gyp,adblockplus/gyp,IllusionRom-deprecated/android_platform_external_chromium_org_tools_gyp,yinquan529/platform-external-chromium_org-tools-gyp,bnq4ever/gypgoogle,android-ia/platform_external_chromium_org_tools_gyp,openpeer/webrtc-gyp,channing/gyp,alexcrichton/gyp,azunite/gyp_20150930,xin3liang/platform_external_chromium_org_tools_gyp,ttyangf/pdfium_gyp,Omegaphora/external_chromium_org_tools_gyp,cysp/gyp,enkripsi/gyp,sanyaade-teachings/gyp,mgamer/gyp,sdklite/gyp,svn2github/kgyp,duanhjlt/gyp,android-ia/platform_external_chromium_org_tools_gyp,pyokagan/gyp,tarc/gyp,svn2github/kgyp,kevinchen3315/gyp-git,saghul/gyn,Phuehvk/gyp,adblockplus/gyp,bnoordhuis/gyp,sanyaade-teachings/gyp,xin3liang/platform_external_chromium_org_tools_gyp,MIPS/external-chromium_org-tools-gyp,chromium/gyp,mistydemeo/gyp,AWhetter/gyp,duanhjlt/gyp,pandaxcl/gyp,Phuehvk/gyp,dougbeal/gyp,carlTLR/gyp,mgamer/gyp,Danath/gyp,trafi/gyp,Jack-Q/GYP-copy,pyokagan/gyp,sanyaade-teachings/gyp,channing/gyp,geekboxzone/lollipop_external_chromium_org_tools_gyp,okwasi/gyp,trafi/gyp,bpsinc-native/src_tools_gyp,bdarnell/gyp,pyokagan/gyp,brson/gyp,okumura/gyp,alexcrichton/gyp,turbulenz/gyp,Danath/gyp,LazyCodingCat/gyp,bnoordhuis/gyp,sport-monkey/GYP,mapbox/gyp,bnoordhuis/gyp,AWhetter/gyp,pandaxcl/gyp,msc-/gyp,okwasi/gyp,brson/gyp,lukeweber/gyp-override,AOSPU/external_chromium_org_tools_gyp,Chilledheart/gyp,clar/gyp,Chilledheart/gyp,turbulenz/gyp,chromium/gyp,cchamberlain/gyp,mgamer/gyp,saghul/gyn,springmeyer/gyp,springmeyer/gyp,omasanori/gyp,amoikevin/gyp,turbulenz/gyp,azunite/gyp_20150930,alexcrichton/gyp,bpsinc-native/src_tools_gyp,IllusionRom-deprecated/android_platform_external_chromium_org_tools_gyp,kevinchen3315/gyp-git,LazyCodingCat/gyp,turbulenz/gyp,cysp/gyp,android-ia/platform_external_chromium_org_tools_gyp,sdklite/gyp,azunite/gyp,Phuehvk/gyp,saghul/gyn,sloanyang/gyp,mumble-voip/libmumble-gyp,yinquan529/platform-external-chromium_org-tools-gyp,svn2github/kgyp,pandaxcl/gyp,erikge/watch_gyp,azunite/gyp,azunite/gyp,sanyaade-teachings/gyp,bpsinc-native/src_tools_gyp,svn2github/kgyp,adblockplus/gyp,mumble-voip/libmumble-gyp,luvit/gyp,Danath/gyp,mistydemeo/gyp,sdklite/gyp,yangrongwei/gyp,geekboxzone/lollipop_external_chromium_org_tools_gyp,Omegaphora/external_chromium_org_tools_gyp,sport-monkey/GYP,mumble-voip/libmumble-gyp,ttyangf/pdfium_gyp,mistydemeo/gyp,bulldy80/gyp_unofficial,sport-monkey/GYP,bnq4ever/gypgoogle,ttyangf/gyp,msc-/gyp,MIPS/external-chromium_org-tools-gyp,clar/gyp,sport-monkey/GYP,chromium/gyp,msc-/gyp,Omegaphora/external_chromium_org_tools_gyp,erikge/watch_gyp,lianliuwei/gyp,AWhetter/gyp,ryfx/gyp,springmeyer/gyp,enkripsi/gyp,amoikevin/gyp,chromium/gyp,geekboxzone/lollipop_external_chromium_org_tools_gyp,pyokagan/gyp,mkrautz/gyp-libmumble,ryfx/gyp,clar/gyp,sloanyang/gyp,mapbox/gyp,pandaxcl/gyp,Jack-Q/GYP-copy,azunite/gyp,openpeer/webrtc-gyp,mapbox/gyp,sdklite/gyp,azunite/gyp_20150930,svn2github/kgyp,tarc/gyp,trafi/gyp,carlTLR/gyp,okumura/gyp,clar/gyp,bnq4ever/gypgoogle,bdarnell/gyp,msc-/gyp,MIPS/external-chromium_org-tools-gyp,mgamer/gyp,ttyangf/pdfium_gyp,adblockplus/gyp,cysp/gyp,tarc/gyp,enkripsi/gyp,springmeyer/gyp,bulldy80/gyp_unofficial,Omegaphora/external_chromium_org_tools_gyp,duanhjlt/gyp,lukeweber/gyp-override,erikge/watch_gyp,mistydemeo/gyp,lianliuwei/gyp,ryfx/gyp,openpeer/webrtc-gyp,duanhjlt/gyp,ttyangf/pdfium_gyp,carlTLR/gyp,yangrongwei/gyp,okumura/gyp,dougbeal/gyp,lianliuwei/gyp,mgamer/gyp,yinquan529/platform-external-chromium_org-tools-gyp,carlTLR/gyp,openpeer/webrtc-gyp,ttyangf/gyp,omasanori/gyp,kevinchen3315/gyp-git,luvit/gyp,kevinchen3315/gyp-git,omasanori/gyp,tarc/gyp,sdklite/gyp,mkrautz/gyp-libmumble,saghul/gyn,bnoordhuis/gyp,xin3liang/platform_external_chromium_org_tools_gyp,tarc/gyp,AWhetter/gyp,IllusionRom-deprecated/android_platform_external_chromium_org_tools_gyp,Phuehvk/gyp,bulldy80/gyp_unofficial,erikge/watch_gyp,msc-/gyp,LazyCodingCat/gyp,geekboxzone/lollipop_external_chromium_org_tools_gyp,dougbeal/gyp,channing/gyp,openpeer/webrtc-gyp,lianliuwei/gyp,xin3liang/platform_external_chromium_org_tools_gyp,erikge/watch_gyp,AOSPU/external_chromium_org_tools_gyp,clar/gyp,yjhjstz/gyp,Jack-Q/GYP-copy,amoikevin/gyp,Chilledheart/gyp,trafi/gyp,amoikevin/gyp,saghul/gyn,cysp/gyp,dougbeal/gyp,AOSPU/external_chromium_org_tools_gyp,mkrautz/gyp-libmumble,duanhjlt/gyp,cchamberlain/gyp,enkripsi/gyp,yangrongwei/gyp,yjhjstz/gyp,channing/gyp,MIPS/external-chromium_org-tools-gyp,AOSPU/external_chromium_org_tools_gyp,LazyCodingCat/gyp,bnq4ever/gypgoogle,ttyangf/gyp,turbulenz/gyp,luvit/gyp,okumura/gyp,svn2github/gyp,sloanyang/gyp,okwasi/gyp,yjhjstz/gyp,yjhjstz/gyp,Phuehvk/gyp,Chilledheart/gyp,bulldy80/gyp_unofficial,bdarnell/gyp,svn2github/gyp,ryfx/gyp,sloanyang/gyp,pyokagan/gyp,svn2github/gyp,cysp/gyp,lukeweber/gyp-override,Jack-Q/GYP-copy,mumble-voip/libmumble-gyp,Danath/gyp,bpsinc-native/src_tools_gyp,cchamberlain/gyp,bnoordhuis/gyp,android-ia/platform_external_chromium_org_tools_gyp,carlTLR/gyp,yangrongwei/gyp,alexcrichton/gyp,dougbeal/gyp,okwasi/gyp,luvit/gyp,azunite/gyp_20150930,cchamberlain/gyp,azunite/gyp_20150930,pandaxcl/gyp,mapbox/gyp,bnq4ever/gypgoogle,brson/gyp,AWhetter/gyp,yinquan529/platform-external-chromium_org-tools-gyp,sport-monkey/GYP,lukeweber/gyp-override,Danath/gyp,IllusionRom-deprecated/android_platform_external_chromium_org_tools_gyp,svn2github/gyp