Add new build.h macro BOTAN_TARGET_OS_IS_XXX
Add new build.h macro BOTAN_TARGET_OS_IS_XXX

randombit/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,randombit/botan,randombit/botan,webmaster128/botan,randombit/botan,webmaster128/botan,Rohde-Schwarz-Cybersecurity/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,Rohde-Schwarz-Cybersecurity/botan