File not recognized: File truncated GCC error

Just remove the object file.

This error most likely appeared after the previous build was interrupted and object file was not generated completely.

I think

g++  -o "hello"  ./src/hello.o  
should be ./src/hello.(c | cpp | cc depending on your language type)

Just as an info if someone comes around here.

Another problem (with the same error) could be, that you are using ccache for faster compilation. In this case, the corrupt *.o file is there as well. So for that reason you have to clean the cache with

ccache -C (note the upper case C!)

Wasted me hours the first time ;-)