What role is 'yang' playing in this sentence. Is it like who was it that built this school?

Etymology [membangun]

mem- +‎ bangun

Verb

membangun (passive dibangun)

1) to build, to construct, to build up

Verba

membangun (me- + bangun; pasif: ku/kau/dibangun, terbangun)

KELUARGA KATA

bangun, membangun, membanguni, membangunkan, kebangunan, bangun-bangun, bangunan, pembangun, pembangunan

membangun [KAMUS SEASITE]

bangun : : : Berdiri dari duduk, tidur, pingsan, dll.

Definisi Singkat : wake up; get up. BER-: get up. MEM-: build, construct. Also MEM--KAN, +

Definisi Inggris : • 1 wake up. 2 get up. BER-: get up. *MEM-: build, construct. *MEM--KAN: 1 wake s.o. up. 2 build, erect. *TER-: awaken (suddenly). *-AN: 1 building, structure. 2 construction. *PEM--AN: 1 (re)construction. 2 development.

Contoh : Saya harus BANGUN pagi-pagi. => I have to GET UP early in the morning.

Walaupun selalu jatuh, ayam jago itu tetap berusaha untuk BANGUN. => Although he always fell, that fighting cock kept trying to GET UP. // Note *1

Indonesia sedang MEMBANGUN di segala bidang. => Indonesia is in the process of DEVELOPING all of its sectors.

Sulit sekali MEMBANGUNKAN adik pagi-pagi. => It is very difficult to WAKE UP (my younger sister/brother) early in the morning.

Tukang kayu itu akan MEMBANGUN rumah baru Bu Hadi. => That carpenter is going to BUILD Mrs. Hadi's new house.

Hampir setiap malam, Karjo selalu TERBANGUN dari tidurnya. => Almost every night, Karjo is AWAKENED from his sleep.

Ada BANGUNAN baru disebelah rumahku. => There is a new BUILDING at the side of my house.

PEMBANGUNAN jalan kereta api akan diteruskan sampai tahun depan. => The CONSTRUCTION of the railroad will be continued until next year.

Source:

Wiktionary

Wiktionary bahasa Indonesia

https://en.wiktionary.org/wiki/membangun

https://id.wiktionary.org/wiki/membangun

http://kamus.sabda.org/kamus/membangun

Note:

*1) I think the English translation of the example (contoh) sentence would be Although it always fell, that fighting cock kept trying to get up.

"Membangun" sounded weird to me, almost like "membedangun". This is only in full speed audio. The slower audio sounded fine.