Add Boost requirement to README

README.md

@@ -25,6 +25,7 @@ The following components are mandatory for building HPVM:
 - GCC (>=5.1)
 - CMake (>=3.17)
 - GNU Make (>=3.79) or Ninja (>=1.10)
+- Boost (on Ubuntu the package `libboost-all-dev` satisfies this requirement)
 
 ### Building HPVM