Why will there be issues while trying to build the Boot to Gecko (B2G) project on my x86-64 Ubuntu 12.10 system. The Gecko build fails when attempting to link `librt`, even though the library is present on my system.

When running the build command for Gecko:

$ ./build.sh -j1 gecko

The error occurs during the linking step:

TEST-PASS | check-sync-dirs.py | /home/user/src/MOZILLA/B2G/gecko/js/src/config <= /home/user/src/MOZILLA/B2G/gecko/config
/home/user/src/MOZILLA/B2G/prebuilt/linux-x86/toolchain/i686-android-linux-4.4.3/bin/../lib/gcc/i686-android-linux/4.4.3/../../../../i686-android-linux/bin/ld: cannot find -lrt
collect2: ld returned 1 exit status

I expected the build process to complete successfully, as the necessary libraries, including `librt`, are present on my system.

The linker (`ld`) fails to find `librt` despite the library being installed. The following command shows that `librt.so` exists in several locations:

$ locate librt.so

/home/user/src/MOZILLA/B2G/prebuilt/linux-x86/toolchain/i686-linux-glibc2.7-4.4.3/sysroot/usr/lib/librt.so
/home/user/src/MOZILLA/B2G/prebuilt/linux-x86/toolchain/i686-linux-glibc2.7-4.4.3/sysroot/usr/lib/librt.so.1
/home/user/src/MOZILLA/B2G/prebuilts/gcc/linux-x86/host/i686-linux-glibc2.7-4.6/sysroot/usr/lib/librt.so
/home/user/src/MOZILLA/B2G/prebuilts/gcc/linux-x86/host/x86_64-linux-glibc2.7-4.6/sysroot/usr/lib/librt.so
/lib/i386-linux-gnu/librt.so.1
/lib/x86_64-linux-gnu/librt.so.1
/usr/lib/x86_64-linux-gnu/librt.so

Despite the presence of the library in both `x86_64` and `i386` directories, the build fails to locate `librt`.

Just worried why the linker is unable to find `librt` even though it’s installed and located in the system, any help?