gst-build permission

Hi，
I used the gst-build project to compile the 1.16.2 version of gst.
The installation path is set to the install directory under the current
directory(belonging to the user's home directory, not the system directory).

> mkdir build meson -Dprefix=`pwd`/install -Dbuildtype=debug -Dvaapi=enabled
>
When installing, permissions are required:

> Installation failed due to insufficient permissions.
> Attempt to use /usr/bin/sudo to gain elevated privileges? [y/n]
>
Select n to exit with an error, and select y to continue the installation.
What I want to know is:
1. The installation target is the current directory, why is sudo permission
required?
2. Will continuing the installation after obtaining sudo permissions modify
the system environment? For example, if some files are modified