Stuck building Gimp from source

Software GIMP
60

our opensuse %meson macro does:

    export LANG=C.UTF-8                      
    export CFLAGS="${CFLAGS:--fmessage-length=0 -grecord-gcc-switches -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -g}"     
    export CXXFLAGS="${CXXFLAGS:--fmessage-length=0 -grecord-gcc-switches -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -g}" 
    export FFLAGS="${FFLAGS:--fmessage-length=0 -grecord-gcc-switches -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -g}"     
    export FCFLAGS="${FCFLAGS:--fmessage-length=0 -grecord-gcc-switches -O2 -Wall -D_FORTIFY_SOURCE=2 -fstack-protector-strong -funwind-tables -fasynchronous-unwind-tables -fstack-clash-protection -g}"   
    /usr/bin/meson                              \
        --buildtype=plain                   \
        --prefix=/usr                 \
        --libdir=/usr/lib64                 \
        --libexecdir=/usr/lib         \
        --bindir=/usr/bin                 \
        --sbindir=/usr/sbin               \
        --includedir=/usr/include         \
        --datadir=/usr/share               \
        --mandir=/usr/share/man                 \
        --infodir=/usr/share/info               \
        --localedir=/usr/share/locale      \
        --sysconfdir=/etc         \
        --localstatedir=/var   \
        --sharedstatedir=/var/lib \
        --wrap-mode=nodownload    \
        . build \

so @Elle was actually correct just instead of the -Dprefix=... you need --prefix=...