Qemu: igvm support: include path from pkgconfig not used everywhere

[osteffenrh]

I get a build error, when the IGVM C library is not installed system-wide.
It seems the include paths indicated by pkgconfig are not picked up correctly for all
compilation units. For example backends/igvm.c builds, but then it fails later at target/i386/sev.c.

I probably did not hit this until now and assumed the pkgconfig detection works fine, because
I had an old left-over igvm.h around in the system ...

$ PKG_CONFIG_PATH=$HOME/igvm/lib64/pkgconfig ./configure [...]
$ make

[...]

[1580/2774] Compiling C object libqemu-x86_64-softmmu.fa.p/target_i386_sev.c.o
FAILED: libqemu-x86_64-softmmu.fa.p/target_i386_sev.c.o
cc -m64 -mcx16 -Ilibqemu-x86_64-softmmu.fa.p -I. -I.. -Itarget/i386 -I../target/i386 -Iqapi -Itrace -Iui -Iui/shader -I/usr/include/pixman-1 -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/sysprof-6 -fdiagnostics-color=auto -Wall -Winvalid-pch -Werror -std=gnu11 -O2 -g -fstack-protector-strong -Wundef -Wwrite-strings -Wmissing-prototypes -Wstrict-prototypes -Wredundant-decls -Wold-style-declaration -Wold-style-definition -Wtype-limits -Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers -Wempty-body -Wnested-externs -Wendif-labels -Wexpansion-to-defined -Wimplicit-fallthrough=2 -Wmissing-format-attribute -Wno-missing-include-dirs -Wno-shift-negative-value -Wno-psabi -Wshadow=local -isystem /home/osteffen/work/svsm/coconut/qemu/linux-headers -isystem linux-headers -iquote . -iquote /home/osteffen/work/svsm/coconut/qemu -iquote /home/osteffen/work/svsm/coconut/qemu/include -iquote /home/osteffen/work/svsm/coconut/qemu/host/include/x86_64 -iquote /home/osteffen/work/svsm/coconut/qemu/host/include/generic -iquote /home/osteffen/work/svsm/coconut/qemu/tcg/i386 -pthread -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -fno-strict-aliasing -fno-common -fwrapv -fPIE -isystem../linux-headers -isystemlinux-headers -DNEED_CPU_H '-DCONFIG_TARGET="x86_64-softmmu-config-target.h"' '-DCONFIG_DEVICES="x86_64-softmmu-config-devices.h"' -MD -MQ libqemu-x86_64-softmmu.fa.p/target_i386_sev.c.o -MF libqemu-x86_64-softmmu.fa.p/target_i386_sev.c.o.d -o libqemu-x86_64-softmmu.fa.p/target_i386_sev.c.o -c ../target/i386/sev.c
In file included from ../target/i386/sev.h:21,
                 from ../target/i386/sev.c:29:
/home/osteffen/work/svsm/coconut/qemu/include/exec/confidential-guest-support.h:27:10: fatal error: igvm/igvm.h: No such file or directory
   27 | #include "igvm/igvm.h"
      |          ^~~~~~~~~~~~~
compilation terminated.
[1581/2774] Compiling C object libqemu-x86_64-softmmu.fa.p/target_i386_cpu-sysemu.c.o
[1582/2774] Compiling C object libqemu-x86_64-softmmu.fa.p/meson-generated_.._qapi_qapi-introspect.c.o
[1583/2774] Compiling C object libqemu-x86_64-softmmu.fa.p/target_i386_kvm_hyperv.c.o
[1584/2774] Compiling C object libqemu-x86_64-softmmu.fa.p/target_i386_kvm_kvm.c.o
FAILED: libqemu-x86_64-softmmu.fa.p/target_i386_kvm_kvm.c.o
cc -m64 -mcx16 -Ilibqemu-x86_64-softmmu.fa.p -I. -I.. -Itarget/i386 -I../target/i386 -Iqapi -Itrace -Iui -Iui/shader -I/usr/include/pixman-1 -I/usr/include/glib-2.0 -I/usr/lib64/glib-2.0/include -I/usr/include/sysprof-6 -fdiagnostics-color=auto -Wall -Winvalid-pch -Werror -std=gnu11 -O2 -g -fstack-protector-strong -Wundef -Wwrite-strings -Wmissing-prototypes -Wstrict-prototypes -Wredundant-decls -Wold-style-declaration -Wold-style-definition -Wtype-limits -Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers -Wempty-body -Wnested-externs -Wendif-labels -Wexpansion-to-defined -Wimplicit-fallthrough=2 -Wmissing-format-attribute -Wno-missing-include-dirs -Wno-shift-negative-value -Wno-psabi -Wshadow=local -isystem /home/osteffen/work/svsm/coconut/qemu/linux-headers -isystem linux-headers -iquote . -iquote /home/osteffen/work/svsm/coconut/qemu -iquote /home/osteffen/work/svsm/coconut/qemu/include -iquote /home/osteffen/work/svsm/coconut/qemu/host/include/x86_64 -iquote /home/osteffen/work/svsm/coconut/qemu/host/include/generic -iquote /home/osteffen/work/svsm/coconut/qemu/tcg/i386 -pthread -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -fno-strict-aliasing -fno-common -fwrapv -fPIE -isystem../linux-headers -isystemlinux-headers -DNEED_CPU_H '-DCONFIG_TARGET="x86_64-softmmu-config-target.h"' '-DCONFIG_DEVICES="x86_64-softmmu-config-devices.h"' -MD -MQ libqemu-x86_64-softmmu.fa.p/target_i386_kvm_kvm.c.o -MF libqemu-x86_64-softmmu.fa.p/target_i386_kvm_kvm.c.o.d -o libqemu-x86_64-softmmu.fa.p/target_i386_kvm_kvm.c.o -c ../target/i386/kvm/kvm.c
In file included from ../target/i386/sev.h:21,
                 from ../target/i386/kvm/kvm.c:34:
/home/osteffen/work/svsm/coconut/qemu/include/exec/confidential-guest-support.h:27:10: fatal error: igvm/igvm.h: No such file or directory
   27 | #include "igvm/igvm.h"
      |          ^~~~~~~~~~~~~
compilation terminated.

[osteffenrh]

(Opening this here, because the qemu repo does not have issues turned on)