Properly quote paths for GCC warnings files (esp8266#8523)

Fixes issue identified by @jjsuwa-sys3175 in
esp8266@46190b6#r69649862

Author: earlephilhower

platform.txt

@@ -68,18 +68,18 @@ compiler.cpreprocessor.flags=-D__ets__ -DICACHE_FLASH -U__STRICT_ANSI__ -D_GNU_S
 compiler.libraries.ldflags=
 
 compiler.c.cmd=xtensa-lx106-elf-gcc
-compiler.c.flags=-c {compiler.warning_flags}-gcc -std=gnu17 {build.stacksmash_flags} -Os -g -free -fipa-pta -Werror=return-type -Wpointer-arith -Wno-implicit-function-declaration -Wl,-EL -fno-inline-functions -nostdlib -mlongcalls -mtext-section-literals -falign-functions=4 -MMD -ffunction-sections -fdata-sections {build.exception_flags} {build.sslflags} {build.mmuflags} {build.non32xferflags}
+compiler.c.flags=-c "{compiler.warning_flags}-gcc" -std=gnu17 {build.stacksmash_flags} -Os -g -free -fipa-pta -Werror=return-type -Wpointer-arith -Wno-implicit-function-declaration -Wl,-EL -fno-inline-functions -nostdlib -mlongcalls -mtext-section-literals -falign-functions=4 -MMD -ffunction-sections -fdata-sections {build.exception_flags} {build.sslflags} {build.mmuflags} {build.non32xferflags}
 
 compiler.S.cmd=xtensa-lx106-elf-gcc
 compiler.S.flags=-c -g -x assembler-with-cpp -MMD -mlongcalls "-I{runtime.tools.xtensa-lx106-elf-gcc.path}/include/"
 
-compiler.c.elf.flags=-g {compiler.warning_flags}-gcc -Os -nostdlib -Wl,--no-check-sections -u app_entry {build.float} -Wl,-static "-L{compiler.sdk.path}/lib" "-L{compiler.sdk.path}/lib/{build.sdk}" "-L{build.path}" "-L{compiler.libc.path}/lib" "-Tlocal.eagle.flash.ld" -Wl,--gc-sections -Wl,-wrap,system_restart_local -Wl,-wrap,spi_flash_read
+compiler.c.elf.flags=-g "{compiler.warning_flags}-gcc" -Os -nostdlib -Wl,--no-check-sections -u app_entry {build.float} -Wl,-static "-L{compiler.sdk.path}/lib" "-L{compiler.sdk.path}/lib/{build.sdk}" "-L{build.path}" "-L{compiler.libc.path}/lib" "-Tlocal.eagle.flash.ld" -Wl,--gc-sections -Wl,-wrap,system_restart_local -Wl,-wrap,spi_flash_read
 
 compiler.c.elf.cmd=xtensa-lx106-elf-gcc
 compiler.c.elf.libs=-lhal -lphy -lpp -lnet80211 {build.lwip_lib} -lwpa -lcrypto -lmain -lwps -lbearssl -lespnow -lsmartconfig -lairkiss -lwpa2 {build.stdcpp_lib} -lm -lc -lgcc
 
 compiler.cpp.cmd=xtensa-lx106-elf-g++
-compiler.cpp.flags=-c {compiler.warning_flags}-g++ {build.stacksmash_flags} -Os -g -free -fipa-pta -Werror=return-type -mlongcalls -mtext-section-literals -fno-rtti -falign-functions=4 {build.stdcpp_level} -MMD -ffunction-sections -fdata-sections {build.exception_flags} {build.sslflags} {build.mmuflags} {build.non32xferflags}
+compiler.cpp.flags=-c "{compiler.warning_flags}-g++" {build.stacksmash_flags} -Os -g -free -fipa-pta -Werror=return-type -mlongcalls -mtext-section-literals -fno-rtti -falign-functions=4 {build.stdcpp_level} -MMD -ffunction-sections -fdata-sections {build.exception_flags} {build.sslflags} {build.mmuflags} {build.non32xferflags}
 
 compiler.as.cmd=xtensa-lx106-elf-as